AcceptVersion parameter handled correctly in GetCapabilities KVP requests

Please review this Pull Request. I made some changes regarding compliance to the WPS 1.0 specification (see https://bugzilla.52north.org/show_bug.cgi?id=907). Requesting wrong accepted versions in a getcapabilities request now results in an exceptionreport containing the "VersionNegotiationFailed" exception code.
I also modified the GetCapabilitiesKVP tests to make the right requests and assertions.