Peer2Peer - 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.
Probably not worth changing (there are pros and cons) but rather than define a custom function, I tend to think it's better to define a variable for each element at the top of the file, using `document.querySelector()` or `document.getElementById()` (which is faster). That way, the variable is only ever defined once – and the definition can be clearer, for example with something like `document.querySelector('textarea#constraints')`.