Extension of mapproxy to support new projections,
layers and services (WMTS)
updating for DB table change and new cleanup up apache entries
correcting mapproxy according to feedback:

- improving documentation and README for mapproxy
- removing OSM layers from config
- coping with empty parts in template
- adding missing projections in WMS
- 'default' rewrite rule for all environnment
- optimized apache settings
- only requesting the needed WMTS tiles
- IGN performance optimization
Redesign: all available timestamps, but not use of keyword 'current'
Merge pull request #865 from geoadmin/mom_mapproxy_extension

Mapproxy service extension