Fix error message issue with non-reservable rooms
Fix eAgreement
Remove VT chars when serializing as XML
Better error message if author does not exist
No author link for withdrawn contributions

Also hide the link if the author is not in the author list for some
reason
Consider days/rooms with only blocking bars empty
Fix error on category statistics page
Some PEP8 fixes
Message content for LatexRuntimeException
Don't mix unicode and str when creating ical file
Don't log MaKaCError as unexpected exceptions
Always show exception details for admins
Fix error caused by deleted contribs in author list

Simply skip deleted contributions and authors who have only deleted
contributions (i.e. with no conference assigned)
Fix searching for rooms with equipment
Make email body show up properly in log entries
Add maintenance script to fix missing menu links