SotBE S7: clarify objectives

Indicate which of the oases that are visible under the fog the player
should move toward.
SotBE S8: don't have Gork address himself

Adjust the dialog if Gork is the one discovering the elves.
SotBE S14: add message about Grüü's gold being returned at scenario end

Previously, the gold was returned, but there was no message visible to
the player about it.
Update changelog with SotBE and Micro AI changes