allow the AI to base-walk without restrictions

fixes #2899
add xbuild to travis configuration

to check if we can still compile with MonoDevelop/Visual Studio
d2k balance changes
change infantry default speeds

infantry was complained as being too fast. Agreed.
fix incomplete bridge repair on allies02
Merge pull request #3191 from chrisforbes/allies02-bridge-fix

fixes #3185 incomplete bridge repair on allies02
removed Volkov voices which is actually Romanov from RA2

fixes #3190
removed RA ShipVoice which is identical to VehicleVoice
Lower combat tank defualt speed

They are a bit fast, and the game is a bit fast.
tank +25 HP, -> 350
harkonnen combat tank slower, tougher
Ordos tank slightly slower
quad slightly slower
tank buffed vs. infantry
fixed oversight from previous change to atreides tank gun
Artillery shell buffed vs. concrete
Red Alert AI configuration

building >1 production buildings is bogus as it has no benefit
generic names that describe the build order not fake personality
increase spread of tank shell

Right now they're too easily bogged down by infantry. 

Bazookas remain a strong counter for tanks.
nerf towers

Very OP and make the game too static/ stalemated.
reduced paratrooper cooldown from 280 -> 180 sec.