Fix WMTS requestEncoding
Sort matrixIds by scaleDenominator

We cannot assume that the matrixIds are ordered in the matrixSet. For example, they're not ordered in http://wxs.ign.fr/cle/geoportail/wmts?SERVICE=WMTS&REQUEST=GetCapabilities.
Add an IGN WMTS example
Export ol.tilegrid.TileGrid#getResolutions
Merge pull request #801 from elemoine/ign

Add an IGN WMTS example