Cash/upgrades/balance

First of all, gitIgnore file now ignores debug directory...WOOOHOOOOO
Implemented cash:
Each tower/upgrade has a cost and is deducted
Ogre deaths award cash
Get some cash at begining of round
Upgrades are implemented, feel free to change their look. The last one
flashes for some reason
Tried to do a little bit of balancing with the money.
TODO: traps/bombs, more balance, enable/disable clicking during creep
phase when needed, and implement robot mesh