[Camera] Refactor/rework video recording

[thmsbfft]

Video recording is still experimental (read: busted).
• It performs very badly on hidpi screens because each frame has to be saved to disc.
• Frames can drop because of disc accesses on resource intensive websites.
• FPS is not 100% reliable. Most videos seem to be playing slightly faster that what's recorded.

So far I see two ways of fixing it:

• Changing the API used to capture frames:
desktop-capturer seems promising, working with streams would eliminate disk access problems.

electron/desktop-capturer
Note: might change the way we choose to record mouse cursors or not. See #30.

• Record frames directly to a stream:
Would rely heavily on ffmpeg to do the hard work.

[thmsbfft]

Fixed in 0.2.0. Closing.