CI: Include style plugins when packaging on OSX

(This commit also modifies the obs-ffmpeg module)

The default channel layouts from aac spec are implemented in FFmpeg
native aac encoder as follows:

    AV_CH_LAYOUT_MONO,
    AV_CH_LAYOUT_STEREO,
    AV_CH_LAYOUT_SURROUND,
    AV_CH_LAYOUT_4POINT0,
    AV_CH_LAYOUT_5POINT0_BACK,
    AV_CH_LAYOUT_5POINT1_BACK,
    AV_CH_LAYOUT_7POINT1,

The correspondence of speaker layouts to AV_CH_LAYOUT from FFmpeg is
changed to reflect the previous table.

Although FFmpeg native aac encoder can now encode all the layouts listed
in avutil channel_layout.h (on master), there might be issues with older
FFmpeg binaries.

Note that 2.1 speaker layout will be encoded as AV_CH_LAYOUT_SURROUND
(FL FR FC) because it is not listed as the default layout for three
channels.

This just means some optimizations for LFE channel will not be used by
the encoder which will treat it as an SCE (single channel element).

Closes jp9000/obs-studio#1182

cmake: Fix LuaJIT search

UI: Fix grayed out Copy option in sources context menu

Fixes a bug where the thread local variable "current_lua_script" is not
set when calling script_tick.

(This commit also modifies the frontend-tools module)

Prevents a potential crash when script_log is called by a thread spawned
by a python library.

This fixes a problem introduced in #1050 where the Copy option would
be grayed out when rightclicking a source above the currently selected
source. This also retains the functionality of not having the Copy option
enabled when no source is selected.

CI: Fixes to get OSX packaging working on travis

CI: Fetch RVM gpg key on osx

CI: Fix a ruby issue on travis OSX

CI: Update OSX deps build scripts

CI: Point to newer brew python

Makes it so that the scripting cmake variable ENABLE_SCRIPTING is a user
variable rather than a global internal cmake variable, and defers the
internal global cmake variable to SCRIPTING_ENABLED instead.

Fixing a reference to Rachni theme folder, some minor tweaks and
reverting volume meter foreground colors to original brightness.

Closes jp9000/obs-studio#1169

CI: Install swig and luajit for osx travis

Prevents Python from automatically trying to load from PATH on startup
on windows.  The user should set their Python 3 path themselves.

Prevents the user when detect-amf piped program crashes due to driver
crash.

UI: fix Multiview labels readability

This reverts commit 5cf11d67.