Change PlEscapeCharacter.NP text to expect &np;
Fix space-character-escape-nbs.vtt to have &nbs;
Fix PayloadEscapeCharacter.AmpersandCharacter.

I've fixed it so that it expects the correct text.
Fix PlEscapeChar.AM to load correct vtt.
Fix greater-than-character-escape-g.vtt.

I've changed the cue text of greater-than-character-escape-g.vtt to make
more sense and reflect what the unit test expects. This doesn't invalidate
the test however, it's still testing the correct thing.