Add V3 API samples for flavor-manage,flavor-extra-specs

Partially implements bp v3-api-extension-versioning

Change-Id: I54881677005cc085e5a2a604fc83eb4225ffd5d0
Add flavor-manage,flavor-extra-specs metafiles for api samples

Converts flavor-manage,flavor-extra-specs api sample to create
meta files for api sample docs.
We use this to auto generate the specification document.

Change-Id: I68eceaeb56a6dad82a17191e5f9a6a706c518cd9
Merge pull request #10 from soulxu/add_metafiles_flavor_manage

Add flavor-manage,flavor-extra-specs metafiles for api samples