API Clarity: Documented o.o.y.yang.data.api and o.o.y.yang.data.api.schema packages.

Fully documented o.o.y.yang.data.api.schema package
Partially documented o.o.y.yang.data.api package

Change-Id: Id2721050abee5120165485dec4b38348f37609b1
Signed-off-by: Tony Tkacik <ttkacik@cisco.com>
Merge "API Clarity: Documented o.o.y.yang.data.api and o.o.y.yang.data.api.schema packages."