Check #enhance again if there's more to enhance
More robust spellbook identification
Spell names are quoted in this message
Make this a log instead of an assert
Simplify the publisher by always sending msg_will_response_* etc

    This fixes a problem where no one subscribes to
    respond_difficult_spellbook, so msg_will_respond_difficult_spellbook
    doesn't go out, so TAEB::Action::Read doesn't update spellbook's
    difficulty, so Magus gets stuck trying to read the same difficult
    book over and over again
Improve chargeable (recharge:charge) display
Set difficult_for_int too
Track successful #enhance's