Missing Python Bindings

[josephbirkner]

Currently, the following Python bindings are missing:

• The /locate DataSourceServer callback setter, and the corresponding LocateResponse/LocateRequest structs.
• The Relation APIs.
• The Attribute/Relation (Multi-)Validity Access APIs
• The TileSourceDataLayer filling DataSourceServer callback setter, and the corresponding TileSourceDataLayer structs.
• The onCacheExpired-callback on the datasource.