Docstrings for MetadataProxy and MetadataProxyHandler
Docstrings for MetadataProxy and MetadataProxyHandler

partially implements: blueprint liberty-doc-updates

Change-Id: Id295107c7dd67ef970cd24ccca3870276483dc4b

stackforge/akanda-rug,openstack/akanda-rug,openstack/akanda-rug,stackforge/akanda-rug