Adjust shopkeeper damage fixing

Adjust shopkeeper damage fixing

Allow shopkeeper to remove webs and pits.

Change the damage fix messaging to be more specific when
shopkeeper removes a trap. Before this the message was
"A trap was removed from the floor", which sounds really silly
when it comes to holes.

Change the damage fixing so the shopkeeper will fix one damage spot
at a time (instead of all at once), so it's more like a monster action.

Some code cleanup, splitting into smaller functions.

While doing this, I noticed that shopkeepers don't actually bill
the hero for the damage, but that'll have to be another commit...