Added remote methods to protect users' email

Corrected return value of remote method Post.findSingle
Fixed existing test and closed hole in comments

The tests needed to be rewritten because of the refactoring.

Comments testing on the new, separate comments controller are not yet
implemented.

A security hole was closed. When querying comments through the post
model, a filter could be applied to get user emails. This is not allowed
any longer for anonymous users. Further research needs to be done on
access that authenticated users have.
Added filter to include username in Comment remote method