Toggleable display debug level

[glennmatthews]

Currently the map display includes some "debugging" information (connection vectors and polygons, rooms and passages color-coded by kind) which is useful for developing and debugging but detracts from the mappiness of the display. This should be a user-configurable option, probably with the following settings:

1. Debug (as the current display)
2. Black and white
3. Black and white, with gray "rock" (for printing with less ink)
4. Blue and white for that classic old-school feel

[glennmatthews]

Current code supports options 1 and 3, but they are not directly selectable - option 3 is used by default, and option 1 is used if the overall program debug level (-v) is greater than zero.