Deferrable actions #1206

Any action may now be deferred by setting a timespan in "deferBy"
field (in HH:MM format) and selecting "defer" action result. When
negative hours or minutes outside [0;59] range are set, nothing
happens.
Fix backoffice clicks #1225 (regression from cf08ebe0b8b629f91f8bfdddbfd4f0fecddaeaa3)
Fix patch collision
Merge #1206 to bo-1.6
Clear deferBy value when an action is deffered #1206
Clear deferBy & result even when deferBy is malformed #1206
Fix action assignment bug #1216
Store assignTime for actions #1207