This removes duplicate code that is already in the
start/stop timer functions.

This allows the user to adjust the media slider with the left
and right keyboard arrows. It is currently set to adjust
by 5 second increments.

When there is no media, set the media to the restart state.
Currently, this only affects the VLC source, as the media
source doesn't use the OBS_MEDIA_STATE_NONE, at this time.

The source toolbar allows quick and easy access to properties and
filers, and shows common properties/features of a source type.  For
example, when you select a media source, VLC source, or the slideshow
source, you'll get media controls to control playback of the media.  If
you select a text source you can edit the font, color, or text if
applicable.  Or if you select a capture source, you can select the
display/window/etc to capture for that source.

If the source toolbar is not desired and is viewed as taking up valuable
space in the window, it can be disabled via the view menu.
Co-authored-by: NClayton Groeneveld <claytong1214@gmail.com>
Co-authored-by: NJim <obs.jim@gmail.com>