Allow change of model manifest id

Add support for changing model manifest id.  This
will allow OEMs to easily modify the model
in their device code

The specification of the model manifest ids for the sample
devices will happen in a following CL.
Change-Id: Ic36161b21df82d62233d54dd18b516cbf4fea16c
Reviewed-on: https://weave-review.googlesource.com/1790
Reviewed-by: Paul Westbrook <pwestbro@google.com>
3 files changed