Apply ISO 19115/Amd 1 and /Amd 2

[desruisseaux]

ISO 19115 has two amendments that we should apply, namely:

• ISO 19115-1:2014/Amd 1:2018
• ISO 19115-1:2014/Amd 2:2020

Changes are:

• Addition of a partyIdentifier property in Party.
• Addition of a scope property in SpatialRepresentation.
• Addition of a rangeElementDescription property in SampleDimension.
• Addition of crs and coordinateEpoch properties in MD_ReferenceSystem (currently not provided by GeoAPI).

The new properties are identified by a version=2018 or version=2020 parameter in the @UML tags.

The amendment 2 (last item in above list) does not apply in GeoAPI because ReferenceSystem is defined as the base type of CRS instead than a separated class that may contain CRS. See #57 for more information.