Add ability to generate a csv output file

This adds a 'csv' option in the config file and a '--csv' swtich.
The defaults in 'archmap.py' and the config file are both set to 'no'
to disable the output.

It uses the 'csv' module from the python standard library.
Move output generators into their own functions

Warning! Major internal overhaul! The 'make_gis()' function has
been replaced by 'make_geojson()', 'make_kml()' and 'make_csv()'.

This doesn't change anything externally.