Make catalogtree work with language depending layers sorting

This adresses the bug discussed in [1]. It handles language correctly to keep state of the catalog tree (layers are sorted by name in the catalog returned by the service).

If we decide to adapt the service, then this would need to be addressed differently. So this can/should be considered a temporary hack.

[1] https://groups.google.com/forum/#!topic/re3-dev/GxN8EZOrESM