bitbake: toaster: add project related models

bitbake: toaster: add project related models

We introduce the notion of a project in Toaster as the item
that holds the specification for triggering a build: the set
of layers used, the set of configuration variable values, and
the set of targets to be build.

Builds triggered through Toaster will be associated with a
Project, and they will be configured based on the project
settings at the moment when the build is ordered.

(Bitbake rev: 0bf0251ae05442ae260c6099b389bf765c4fef26)

Signed-off-by: Alexandru DAMIAN <alexandru.damian@intel.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>