Fixed some fields (in particular isVisible) not being reset for destroyed units.

When a unit is destroyed, all fields should reset to inaccessible values.
Fields which are updated in updateInternalData was not reset (visible, detected, player, type, transport, position, hitpoints, resources, build queue slot and isCompleted).
Merge pull request #524 from tscmoo/dev

Fixed some fields (in particular isVisible) not being reset for destroye...