move geo_default_site to site.conf and add some documentation

compatible with gluon v2016.1.x since Apr 28, 2016

update ffho-site-auto-select

pointwithinshape needs {{x=..,y=..}...}

the file has to be stored in $(GLUONSITEDIR)/extra/geo.json and is later stored in /lib/gluon/site-select/geo.json. bevore storing, the data is decoded and encoded to get rid of spaces, comments and line break.

untested
script missing to generate the site-coords.gz

actualy ffho-site-auto-select only discovers the site of batman-neighbour. For that purpose a cron-job ist added during upgrade.