Add parsing of some WMS 1.1.1 specific nodes

This PR add the parsing of `<SRS>` and `<LatLonBoundingBox>` nodes (WMS 1.1.1)

Adds also tests for parsing of a WMS  Getcapabilities 1.1.1 file
wouldn't it make more sense to always return the same member name here? At least that's the approach we took in OpenLayers 2.