Define time period for a functionary position's door-access

[KingJohanna]

The system for tracking people's door-accesses (https://fsektionen.se/admin/dorrar) is currently insufficient since it assumes that a functionary post has its regulated door-accesses for the entire occupation period. The Song Contest Team Leaders for example only have their accesses during the autumn semester (see https://fsektionen.se/dokument/504), but will technically keep their position for the spring semester as well.

The box where the positions are filled could be split into four, for each quarter (läsperiod). This problem only applies to a few positions though, so there should be a "apply to all periods"-function as well.

#1045 is a related issue.