PDF functionality is now read-only. Auto generating pdf's
function to be craeted.

All required actions are determined and saved in `submission.cycle`
now. The actions required are determined at initialization of
the submission. Different cycles now possibly can have different required
actions. All template logic to determine required actions is removed
from the codebase.

This commit contains the removal of html from 'the important' models
 or at least contains replacements for model methods such as `print_as...()`,
 etc. etc. Except for `header_as_li`, methods are not completely deleted yet.

> Fixed/Improved the nested comments and comments in reports. They were
 not shown before.

> Improved DRY principle in several templates/codes.

> Created Managers in the `submissions` app to filter i.e. "pool" submissions
 (so exclude potential author from judging on his own publication) for the
 pool view in the query; not in the template!

> More...

Write tests and refactor html.

Fix bug that allows a forged post request to create a comment,
while the submission is not open for commenting.

Only works for comments on thesis links. All comment forms
should post to this link from now on! (So all logic pertaining
comment creation should disappear from the models' detail view.)

I also added a `new_comment.html` partial template and added tests.

The datepicker behaved weird in firefox, and I think fixing it
has no priority now. I've created the VettedThesisLinkFactory
and wrote a couple of happy-path tests for the theses view.