Increased button sizes on Video.js control bar, to increase touchability

Depends on #474, which depends on #471.

Fixes a UX issue @wangguan59 and @gimick identified a long time ago (but that I can't find an issue for) about it being hard to tap the buttons on the video player on mobile devices. Sizes are increased here.
Also, did you want this branched off of develop or rct2?