Add 'genpoi' command

Add new command 'genpoi' similar to 'list' that outputs dungeon
locations in the POI format used by the Overviewer mapping tool, ready
for inclusion into config.py
Make genpoi output full config file

The genpoi command now outputs a fully valid configuration file rather
than just the POI section
Default markers to be visible in POI file
Add --quiet option and --outputdir for genpoi.

The --quiet option suppresses progress messages.  It still needs to
suppress messages in items.py though
Corrections for POI location functions

Unable to identify room_size but use <<4 instead as this is the same.
This should be close enough.
Merge branch 'sshipway-genpoi' into development
Added genpoi to changelog. Whitespace cleanup.