bind SPACE (or some key) to CAPTURE, *all the time*

[notklaatu]

@cyanidecupcake told me that in classes, the SPACEBAR does not always trigger CAPTURE. This should always, always trigger CAPTURE.

This doesn't break anything, so I'm marking it as an enhancement even though technically it's a bug because it's supposed to be grabbing spacebar all the time.

[cyanidecupcake]

Should definitely always be SPACEBAR, the only other acceptable option would be RETURN, but SPACEBAR is easier for kids to press.

[notklaatu]

1. github bug tracking is bad
2. this bug is marked [INPROGRESS]

[notklaatu]

notes: if showing camera view → space=capture if showing still frame → space=disabled ; playButton=play if playing → space=disabled ; playButton=stop