Merge branch 'talent-lists' into 'master'

Talent lists

    Adds a 'lists' system for convenience. Modified stealth and step up to use.

    This lets talents / effects add themselves to lists at appropriate
    times. Bascially, just a quicker way than searching for all applied
    talents/effects for a specific tag.

    Talents can have a sustain_lists and a learn_lists field.
    Effects just have a lists field.

    Example:
    talent A has the following:
    learn_lists = {'red', {'blue', 'green'}}
    When you learn it, your character now has the following fields:
    self.red = {'T_A'}
    self.blue.green = {'T_A'}

    Modified stealth and step up to use this system. So, to make something
    break when step up does, just add it to the 'break_with_step_up' list.