PLUS : Modified text on buttons
BUG FIX : Being unable to upgrade a tower

* You were unable to upgrade a tower if you have already built on the
spot and destroyed
BUG FIX : Building selection screen was saving

* for example if you chose resources in a building slot, but didn't buy
anything, and then clicked on another building, and then back on the
previous, the state would remain,still displaying available
resource-type buildings
BUG FIX : issues with building states
PLUS : Rework on endless mode