Added test mixin for WCS 2.0 GeoTIFF encoding extension requests. Added test cases and expected responses as well.
Removed not standard format options in favor for geotiff eincoding extension.
Updated expected GetCapabilities responses with new interpolation related info.
Adding tests for various interpolation methods.
Updating expected results for GetCapabilities responses.
Merge branch 'interpolation'
Merge branch 'master' into crs-extension

Conflicts:
	autotest/expected/WCS20CorrigendumGetCapabilitiesEmptyTestCase.xml
	autotest/expected/WCS20GetCapabilitiesEmptyTestCase.xml
	autotest/expected/WCS20GetCapabilitiesValidTestCase.xml
	autotest/expected/WCS20PostGetCapabilitiesValidTestCase.xml
	autotest/expected/WCSVersionNegotiationNewStyleTestCase.xml
	autotest/expected/WCSVersionNegotiationOldStyleTestCase.xml
	autotest/expected/WCSVersionNegotiationTestCase.xml