[WIP] CadastralWebMap WMTs form WMS

Goal ist to offect the layer 'ch.kantone.cadastralwebmap-farbe' also as a WMTS layer. Mapproxy is used to convert to WMTS from the original WMS.

* As the data and the source WMS is update on a regular basis, and we do not want/could update the mapproxy config at the same pace,  we could either use the WMTS keywords 'default' and 'current' or use a timesamp as '00000000' which has no signification
* Perfomance is very dependant from the original WMS server (extern)
* It replace the same layer now in production. (we could not define two backend for the same layer in one GetCapabiities). The timstamps used will be lost, unless we do some url rewriting.
* Access rules, same as native tiles.


Exemple: http://mf-chsdi3.int.bgdi.ch/mom_cadastral_wmts/examples/cadastralwebmap.html