Feature request : allow choosing service type and crs when loading layer

[vijdz]

I'd like to load a layer via WMTS and in 3857, but the only thing I can do with the plugin is to load WMS in native CRS.
It would be great to add a CRS option, because even changing the project CRS cannot do the trick.

Also, it would be better to be able to choose WMTS or use this by default, because since the layer is loaded via WMS and without the TILED parameter, there is no way to make use of the geowebcache tiles.