[Graphics] Map Symbols from California Chapter meeting/Sprint

[Alex Mandel]

While I still haven't gotten around to my symbology database/keywording 
tool yet... a few of us did get together and convert a bunch of symbols 
to svg from pdfs and other not so usable formats (150+symbols).

I've pushed the results to svn, under "sets" because these all come from 
pre-made grouping of iconography created various US gov. agencies and 
are presumable all public domain.
http://svn.osgeo.org/osgeo/graphics/trunk/map-icons/

Under themes I also add the ISO 19115 Topic Category names based on
http://gcmd.nasa.gov/User/difguide/iso_topics.html
So if you happen to make a symbol or two those seem like the best 
(though not great) categories to file them under for now.

Thanks,
Alex