Improve submission & fix model errors

Submission:

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

Model:

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