Patch-related improvements

When a file is submitted the tracker should be able to:

• Determine if the file is a patch or not;
• Determine what files are affected by the patch (and possibly add the module/package names as tags);
• Determine if the patch contains tests, docs, Misc/NEWS entry, Misc/ACKS, etc.;
• Determine if the patch contains trailing whitespace or PEP 8 violations;
• Determine on which branches the patches apply on without conflicts (with a way to re-check it on demand or periodically);