Bot AI: improve bots aim by requiring they aim at the target (with some tolerance...

Bot AI: improve bots aim by requiring they aim at the target (with some tolerance) before starting to shoot (bot_ai_aimskill_firetolerance is now enabled by default). It fixes bots often missing the first shot right when they get a new target if they were aiming in a different direction

To make work bot_ai_aimskill_firetolerance with all weapons, fire tolerance is now raised for specific attacks that don't require too much accuracy, e.g. shotgun and devastator attacks