Implement POST /permissionsets (add & modify)

Signed-off-by: Alexander Berntsen <alexander@plaimi.net>
Signed-off-by: Stian Ellingsen <stian@plaimi.net>
Reviewed-by: Stian Ellingsen <stian@plaimi.net>
Implement GET /permissionsets (ID/timespan/role)

Signed-off-by: Alexander Berntsen <alexander@plaimi.net>
Signed-off-by: Stian Ellingsen <stian@plaimi.net>
Reviewed-by: Stian Ellingsen <stian@plaimi.net>
Implement DELETE /permissionsets (by ID)

Signed-off-by: Alexander Berntsen <alexander@plaimi.net>
Signed-off-by: Stian Ellingsen <stian@plaimi.net>
Reviewed-by: Stian Ellingsen <stian@plaimi.net>
Merge branch 'perms-api'

Conflicts:
	src/Tempuhs/Server.hs
	src/Tempuhs/Server/DELETE.hs

Signed-off-by: Stian Ellingsen <stian@plaimi.net>