Fix bot target height for obelisks

Now they aim at the center of the target model, based on patch by Tobias Kuehnhammer.
Fix notarget cheat

Bots no longer target players in 'no target mode'.
Check if possible bot target is on same team sooner
Improve bot enemy selection involving carrying flag or skulls

bots now decide which enemy to attack, when carrying flags/cubes. Team Arena skulls were missing, this caused silly enemy decisions on space maps with g_gametype 7!
allow targeting enemy farther away if carrying skulls (already the case for carrying flags).
Bot revenge support

Make bots use CHARACTERISTIC_VENGEFULNESS to randomly decide if bot should have revenge on player who killed them.

Based on patch by Tobias Kuehnhammer.
Don't have bot crouch if blocks view of target

Can cause bot to keep switching between crouching and standing.