Implement WCS20 Extensions (#4898)

- Add parsing capabilities for WCS RangeSubset extension.
- Implement WCS geotiff extension.
- Properly implement CRS extension.
- Fix Profile URIs for WCS 2.0
- Fix subsettingcrs KVP parameter name.
- Proper implementation of scale extension.
- Fix index for rangesubset intervals. Also allowing integers as band identifiers.
- Fix geotiff:predictor parameter. Should now be one of 'None', 'Horizontal' or 'FloatingPoint' as required in the spec.