Added a model for the PACKAGECONFIG variable, which has a one to
many relationship with the Recipe model.
Added models for static build dependencies and dynamic build
dependenices, both of which have a many to many relationship with
the Recipe model.
These objects are created in update_layer.py and are displayed on the
Recipe detail page.
Added a depends search option for recipes, allowing users to search for
recipes based on the recipe's build dependencies.
Fixes [YOCTO #12129]
Fixes [YOCTO #11415]
Signed-off-by: Amanda Brindle <amanda.r.brindle@intel.com>