Add OpenLayers 2.13.1
Use OpenLayers for map views

And the OSM nominatim service for geocoding, and the OSM default map.
Split overlay in person and group layer

Also fix up the OpenLayers design a bit
Make Google Maps use optional

The default is GMaps, but the example config sets up OSM.
In case no Google Maps are used, its javascript isn't loaded either.
Maps rework

- remove the person/group buttons.
  Instead, these are now separate layers

- make person layer a vector layer
  This allows collecting clusters of people
  into a single item with a counter

- hide some maps internals
Add addPersons interface to maps

This allows preparing a large set of persons to add in one go,
which performs much better on large data sets (eg. 10k entries)
Make sure dialogs are on top

Sometimes some OSM elements would sneak in front of jquery dialogs