Add a new Project class which is responsible for everything related to
opening and closing audio, video, subtitles, timecodes and keyframes.
This pulls almost everything not directly related to playing audio/video
out of the audio and video controllers, pulls more crap out of
FrameMain, and happens to make things a little simpler in the process.
wx comes very close to just making it work automatically, but it doesn't
translate the origin to the top-right corner and wxBufferedPaintDC
doesn't handle RTL at all, so reimplement it with some hacks.
Closes#1354.
Make the vtables less absurdly huge (knocks 100KB off aegisub32.exe),
eliminate some copies of the values when constructing the options, and
use an enum class for the value type.
The grid needs to be able to map AssDialogue * to a row number, and just
storing it in the AssDialogue is nearly strictly better than a std::map
mapping events to rows. Probably will be of use elsewhere as well.
