Improvements to autoexplore in new build!

Along with some minor bug fixes, I've tried to improve the autoexplore behavior.

In general: If you try to autoexplore and can't because there's a monster in line of sight, the game should helpfully point that monster out to you.

Specifically, exploration has improved in Towers, Fallen Castles, and Graveyards. Your hero will be much less interested in meaningless tiles outside of the main combat area.