[PATCH] Improve handling of mixed gate and long wall selections

[Deiz]

Patch removes the mutual exclusivity between gate locking icons and gate conversion icons. If a selection contains both gates and convertible walls, both types of icons will be shown.

The sort order is dependent on the primary selection. E.g. if the primary selected entity is a gate and the second selected entity is a long wall, the icons will be [Lock] [Unlock] [Convert to Gate]. If the selection were the other way around, it would be [Convert to Gate] [Lock] [Unlock].

I've also opted to highlight both the Lock and Unlock buttons if there are selected gates with both of those states. Clicking one of the buttons will set all selected gates to that state.

[leper]

Commited in r12230.