Geo: make page polygon border thinner

This has been like that in ypart.eu for a while.
Refactor javascript function parameter passing

* use parameter object instead of multiple parameters
* allow to define defaults parameters (through $.extend)
* add helper function to ease transformation from python dicts to
javascript objects
Cleanup geo related docs
pep8
Use adhocracy.config
reorder functions (trivial)
Add type cast parameter to config.get_list
Add config.get_json helper function
Merge branch 'develop' into geo
Make boundary defaults and restrictions configurable
geo: Allow to configure image overlays