Add caption_margins to cutscenes

Closes #850

Margins are calculated as a percentage of the screen size. The format is
`caption_margins=x,y`, where x controls the left/right margins and
y controls the bottom margin. The top margin is ignored since captions
are aligned to the bottom of the screen.
Merge pull request #125 from clintbellanger/master

merge from master
dont render classlist label if classlist hidden
Merge pull request #856 from RyanDansie/gamestatenew_classlist_h

Dont render the classlist label if classlist is hidden
Merge pull request #855 from dorkster/cutscenes

Add caption_margins to cutscenes