source_stream_wfs_3d : full french extent for buildings

[mbredif]

Could this extent be extended(!) to cover the full area where data is available ?

itowns/examples/source_stream_wfs_3d.html

Lines 177 to 180 in 7db9bcb

	west: 4.568,
	east: 5.18,
	south: 45.437,
	north: 46.03,

That would showcase the availability of IGN data everywhere (on French territory).