Resolving various issues in GeoServer

## [GEOS-5993] Missing ElectronicMailAddress in WFS capabilities
In the WFS capabilities there were missing two important fields that are
present in the XSD. Those fields are ElectronicMailAddress and
DeliveryPoint.

This commit adds those two fields, but disregards the fact that there
can be more than one of both fields. However this patch could be adapted
to create a List or Array of both, so they are more faithful to the XSD.

Back link to JIRA: https://jira.codehaus.org/browse/GEOS-5993

## [GEOS-6655] Add text/xml MIME-types to WMS
This commit adds "text/xml" and "text/xml; subtype=gml/3.1.1" MIME-types
to WMS 1.1.1 and 1.3.0. These MIME-types are similar to the already
existing GML2 and GML3.1.1 MIME-types that are already present in
GeoServer.

The main reasons for adding those two MIME-types is 1) compatibility
with the OGC WMS standard, which defines that text/xml should be
expected on a textual output, and 2) supporting the Dutch national
profile for maps. Both documents are linked on JIRA.

Back link to JIRA: https://jira.codehaus.org/browse/GEOS-6655

## [GEOS-6657] WCS schemaLocation lacks namespace
The generated XML files in the WCS module are lacking a namespace in the
schemaLocation attribute, resulting in invalid XML. This commit will fix
this.

Back link to JIRA: https://jira.codehaus.org/browse/GEOS-6657

## [GEOS-6654] XLink moving to 1.1
In WFS 2.0 the wrong Xlink XSD was linked, instead of using the original
W3 Xlink, the old and deprecated OGC Xlink was used.  This change should
not impact further functionality of the WFS module.

Back link to JIRA: https://jira.codehaus.org/browse/GEOS-6654

## Various issues
Fixed the WCSTestSupport class to reflect a path change for the XSD Schema's. This test now runs again.