Add a generic openstack-project software config

All of the openstack projects get built in the same manner, therefore,
just provide a single config to rule them all.  This is generic and
does not provide a "name." This will be supplied by the
omnibus-openstack build.
Rework the configs for omnibus-openstack

I have reworked how omnibus-openstack builds, and these configs are no
longer necessary.
Adding a software config for libffi

As the title suggests, we require libffi for building omnibus-openstack
packages.
Complete rework of the build process

Now we require a manifest file that will tell omnibus-openstack
exactly which projects you care about. If its in the manifest, it
makes it, and if it's not it doesn't.  That manifest may be json or
yaml.

Each project will now be a separate venv within the resulting package.

One package to rule them all.
Add a new top-level openstack project

This new top-level project only includes one dependency: all of the
common requirements via openstack-common. All other dependencies are
added at runtime.