"Same type objects" indicator added and other changes

New:

- An indicator added to already placed turrets and building, so when the player holds the mouse over any button that belongs to a type of building already placed, the indicator will show up around the placed objects. This will greatly help the player to identify where he placed certain turrets and buildings.

Changes:

- Deposits no longer have mineral limits. As long as there is a mine on them, the mine will generate minerals.

- Iron ore refinery now displays the liquid iron effect when there is at least 1 iron ore available, instead of when there is an iron ore mine built.

- Camera down rotation increased due to player feedback.

- Camera lo nonger slides on the ground or in the air when the zooming reaches the minimum or maximum allowed value.

- Iron ore mine's button's image fixed.