Improve submission & fix model errors

Submission:

• Change default behavior for interest indication (#198 (closed))
• Fix & improve wiki link generation and disable editing of the link in frontend (#193 (closed) and #204 (closed))
• Restrict AKSlot duration to length of the event (#212 (closed))
• Hide requirements field in AK submission form if no requirements are modelled for the event (#199 (closed))

Model:

• Fix room availability editor (#191 (closed))
• Fix docstring format issue