V4.8.6 CREATE ENTRANCE PERSISTENT

Same transition screen as V4.8.5.

CREATE ENTRANCE IN MAP = place a new entrance.
ADD / UPDATE ENTRANCE = commit it.
Once committed, that entrance stays.
After commit, the editor automatically prepares a fresh blank entrance slot.
Entrance 2 does not remove entrance 1.
Entrance 3 does not remove entrances 1 and 2.
Repeat indefinitely.
Only Delete selected entrance removes an entrance.
