The workarounds were made because of conflicts with running multiple UI
threads at once on macOS, which macOS can't do very well, and would be
susceptible to crashes.  This would cause crashes not only on startup
but seemingly at random when using the browser source on macOS.  The
original "fix" was a hack to try to minimize UI code and browser UI code
from executing at the same time.  The macOS initial scene loading was
deferred until all Qt-related and main window initialization was
completed.  Although this worked to some extent to prevent conflicts, it
made it so that there was an initial period on startup where the entire
UI seemed "blank" for users, and it was still possible for the main UI
thread and the browser UI thread to clash, causing crashes seemingly at
random for users.

The external message pump method of CEF is the solution to the problem,
which is the method which allows the main UI thread to share events with
CEF.  To do this, all CEF operations need to be performed in the UI
thread (Qt's main thread), and CefDoMessageLoopWork() needs to be called
when CefApp::OnScheduleMessagePumpWork callback is triggered.  A number
of other issues had to be solved as well, such as CefBrowser references
getting "stuck" in the Qt event queue.

With this, macOS no longer needs to do the "deferred load" hack, and
browsers are now much more stable and no longer as susceptible to
seemingly random crashes, improving overall program stability when
browsers are used.

Fixes https://obsproject.com/mantis/view.php?id=1443

The message boxes that tell you that the browser is initializing or that
you're authenticating with twitch are annoying on startup.  It makes
sense to do it in the settings/autoconfig dialogs where you sort of need
to know what's going on while waiting for it to connect, but on startup
it's not really necessary and can be kind of annoying.

Additionally, check for null output handlers.

If the user doesn't use the auto-configuration on first use, set the
default encoders used in simple output mode to hardware encoders.

Adds the ability to connect/login to an account via the settings and
auto-configuration dialogs.  Checks registered Auth objects, and if the
Auth object matches the currently selected service in the settings
window or auto-configuration dialog, will display "connect account"
buttons for the user to be able to click (which are optional, they can
still use stream keys if they'd prefer).

Allows the ability to authenticate to a specific service.  Typically via
OAuth.

Adds a function for initializing browser and cookies in a separate
thread while, and while waiting for it to complete, show a dialog
stating that the browser is currently being loaded.  Allows the ability
to safely prevent the user from taking any action without actually
freezing up the UI thread.

Allows the ability to switch cookies between profiles.  Allows the
ability to, for example, switch streaming service accounts between
profiles for proper access to the pages displayed by the browser panels
(such as chat windows).

Adds OBSBasic::Get() to just quickly return the main window.

* UI: Fix mem leak with projectors

* UI: Fix mem leak with ScaleFilteringMenu

* UI: Fix mem leak with sourceProjector

* UI: Fix leak with preview projector in Source menu and Preview

* UI: Fix mem leaks with background color menu

* UI: Fix leak with deinterlace Menu

* UI: Fix leak with scene transition override menu

* UI: Fix leak with scene projector menu

* UI: Fix leak with filter shortcut in Main

* UI: Fix leak with filter shortcut in stats

Closes obsproject/obs-studio#1304

On KDE and Unity some QT events aren't triggered as explicit stated
by QT doc.  This is needed to at least show a fixed Context Menu.

Closes obsproject/obs-studio#1252

The stats dock was incorrectly added to the .ui file, causing the stats
dock to show by default on startup, and just generally causing a bad
default startup UI appearance.  This fixes that by adding the stats dock
programmatically/dynamically instead of modifying the .ui file.

Closes obsproject/obs-studio#1343

Fixes a bug where removing quick transitions with no hotkey would
unintentionally remove the "start streaming" hotkey.  Hotkeys must be
initialized to OBS_INVALID_HOTKEY_ID (-1) instead of 0.  Hotkeys should
really be one-based rather than zero-based.

QNetworkReply was added here in commit
5ba8b09c. Qt5Network was replaced in
commits 13bed1a4 and
39d1cda4, but this one line referring to
QNetworkReply remained. Let's finally remove it.

This commit adds the ability to select a background color for a
scene-item, whether it's a custom color or one of eight presets.

As this is an initial implementation, it lacks theme customizability,
and it also lacks the ability for the user to set their own preset
colors, so only the hard-coded 8 are available.

Contrary to what the name would have you believe, QPointer<> is not used
to delete a pointer when it leaves its specific scope.  Instead, it's
used to check to see if the pointer is still valid.  For most
QWidget-based objects, this is actually fine because QWidgets that are
assigned to layouts or other widgets will automatically be destroyed --
however, for non-widget objects, this can cause a memory leak.

This patch replaces QPointer with QScopedPointer where applicable to
prevent memory leaks.

Closes obsproject/obs-studio#1367

This adds a confirmation dialog for streaming or recording if
there are no sources.

Closes obsproject/obs-studio#1344

Allows the ability to show a web page via CEF to the users on startup to
present and announce new features.

Because sub-items of groups can no longer reroute their signals to the
parent scenes of groups, delegates removal handling to SourceTreeItem
instead of OBSBasic.

When the vertical volume meter was introduced it set in the OBSBasic.ui
mixer dock definition a min width/height that was valid for both
widgets. QStackedWidget hints the minimum size as the higher w/h
of its children so this workaround is necessary.