Add video playback with subtitles via "Universal Media Player" Unity plugin (based on VLC media player)

[drojf]

WIP placeholder in case we ever add this feature to the main mod

Portalboy in the discord wanted to add video playback with subtitles for their translation (?), so they made a prototype using "Universal Media Player" plugin v2.0.3(?) (which uses VLC media player libraries internally).

Notably this should be able to play more video formats (so we don't need to re-encode), although I haven't tested it on any of the original movie files from various sources.

They gave me this prototype, and long story short I integrated it into the mod.

However I've only tested it on Windows, not Mac or Linux...I don't actually know how it's supposed to work tbh.

But since I got it working on Windows I thought I should raise a PR here.

Of note:

• do not directly merge this PR. It includes a huge number of DLLs, so the complete configuration is recorded for safekeeping (for now). In the past we put the DLLs in the repo, but I don't think it's a good idea, we should distribute it separately.
• The added code is from the Portalboy's decompiled project, not from the source code (which we have). Could put in actual code so it is formatted correctly and you have comments, but I guess since it's library code it doesn't matter
• I have modified the library code. Perhaps can get away without doing that but I haven't tidied up yet
• I haven't tidied up the code yet.
• The only form of documentation was this PDF
  UMPManualEng.pdf
• Font rendering MUST have hardware decoding disabled, see 705229b
• Probably heaps of other gotchas I can't remember right now