Merge pull request #359 from bbinet/useTile-consistent

Be more consistent with useTile parent method
Using a server that is not down

fix #353
Merge pull request #360 from ahocevar/demo_dot_opengeo_dot_org

Using a server that is not down. r=@elemoine
Move factorizable code in ol.TileUrlFunction.expandUrl
Remove expandUrl duplicated code from createFromTemplate

and make use of expandUrl function instead.
Try to expand single url for TiledWMS source
Homogenize wmts tileUrlFunction relative to other sources