Use YAML+templates to define deb pkg builds

Use YAML+templates to define deb pkg builds

Adds deb pkg building helper script

The build.py script uses templates/build_debianfiles.py to
generate debian files for ODL .deb packages. To execute script:

  $ build.py -v <version_major> <version_minor> <version_patch> \
                <pkg_version>

build_debianfile.py reads build_vars.yaml and uses Jinja2 templates to
create debian files specific to a build.

The directory `templates` contains jinja2 templates for files
debian/control, debian/rules, debian/changelog. These files change
dynamically for every build. The other files are mostly the same for all
builds.

Also installs Python dependencies for build scripts in Vagrant env and
adds information in README.markdown for building Debs.

Change-Id: Iabba1d808c4fbb4a5832556c30dca4f9de13aaa4
Signed-off-by: Akshita Jha <zenith158@gmail.com>
Signed-off-by: Daniel Farrell <dfarrell@redhat.com>