This adds support for JSONSchema style property declarations with nested
schemas. This is a step towards using more nested structured for
configuration, rather than adding to the over 700 keys already defined
in the main config schema.
Defaults from property schemas are aggregated into a default value in
the top level schema. Descriptions are however not yet aggregated.
Change-Id: Iaf46a9ecc83bee3566098c56137a1be66bff2ab9
