Add build profiles to build.py

Add ability to define "profiles" in kolla-build.conf, which are
predefined sets of images to build at once.

The supplied profiles match what Steven defined in the
restructure-template bp, though others can easily be added by the user.

Multiple profiles can be supplied at once, as well as supplemented by
the existing regex mechanism, e.g. to build profiles infra, main, and
also ironic, one can use:

tools/build.py --profile infra --profile main ironic

Change-Id: I0c6f450152cb23dcfc58e0969669fcedf03fab01
Implements: bp restructure-template
Doc-Impact