cwmp: Add Ghn data model for GFLT400

Implements most of the G.hn parameters defined in
catawampus/tr/schema/tr-181-2-4-0.xml

Parameters are pulled from /tmp/ghn/config (go/fibercl/83381)
See go/gflt400-data-model for more details.

Change-Id: Id5624697218903f51894b125d63e9c5c163320a7
4 files changed