Fixed dehydration not working on embellished desert
Fixed duplicate unit id's by PLACE_UNITS_RANDOMLY
Fixed issues in MOBILIZE_SIDE

The unit re-creation method caused things like HP mismatch due to the
original unit having traits but not the re-created. It was also
needlessly verbose when a simple store/unstore does the job.
Allow visible guardian units to be dehydrated
Remove immediate dehydration of spawned ogres

Either the bandits and castle ogres should receive it too, or none, and
I opted for none.