Talent speed

• Adds the optional 'speed' field to talents, which will change how much energy they use.
• Adds the optional 'display_speed' field to talents, which will change what is displayed under 'Usage Speed' in the talent description.
• The default 'Usage Speed' line in the talent description displays the speed type and the % of a turn it will use, accounting for the actor's current speed bonuses. (eg. "Usage Speed: Spell (100% of a turn)", or "Usage Speed: Weapon (90% of a turn)" with a 'quick' weapon.)
• Changed a few talents that don't use any speed to use one. (Dirty Fighting, Ambush tree)