Fixed all JSHint errors which wont affect (mostly) the planned refactor to classes + some tidying

Fixed all JSHint issues except [1].
Changed all comments to // in favor of /*. 
Removed @private comments.
Added 'use strict' + fixed the errors.
Changed to use equality operators and typeof().

The remaining JSHint errors [1]  will be taken care of when it's rewritten as classes.
[1] - Snippet of errors:

Bad option: 'global'.
eval can be harmful.
'MediaStreamTrack' is not defined.
'getUserMediaFromHere' is defined but never used.