[Mapserver-inspire] Named group layers via "wms_layer_group"

[Stephan Meißl]

Hi all,

I've been working on some INSPIRE related stuff and recently added some
features in the INSPIRE sandbox [1].

The most important one is maybe initial support for named group layers
via "wms_layer_group" (cf. #1632). A group in "wms_layer_group" is
treated as a named one if an actual layer with the same name exists.
Otherwise you get the old behavior of a non-named group. This metadata
key is taken into account in GetCapabilities, GetMap, GetLegendGraphic,
GetStyles, DescribeFeature, and GetFeatureInfo operations. Please have a
look at it and highlight any omission, bug, etc.

Note also the minor change to use "." instead of "_" for language
metadata key extension e.g. "wms_title.eng".

Thanks for your feedback,
Stephan

[1] http://trac.osgeo.org/mapserver/changeset/12940