Move all tchap code in single dir - for linting, and because it's clearer

[estellecomment]

Things would be simpler if all tchap code was in a single directory, so that we would only lint our own files. See this PR : #383

Also nice for devs to understand which code is which : element's code and ours are mixed so if you weren't the one to write the files, you don't know if they're tchap or element.

[odelcroi]

all js code has been moved to a single src/tchap single directory