Support for accepting paste submissions after deadline

When paste is submitted after deadline and all test have passed, no points are given, and following notification is shown:
![screen shot 2014-09-25 at 23 46 16](https://cloud.githubusercontent.com/assets/1354151/4412856/78a2040e-44fd-11e4-9327-5f734d91e255.jpg)

Maybe add note here that this will be a pastebin-only submission, if that is the case. For bonus points, force the paste checkbox to be checked and greyed out in that case.