Convert Kolla to installable Python package

Now the scripts for building images, generating env variables, running Kolla etc. are (in majority) inside tools/ directory and they are not installed anywhere - they have to be run explicitly from the directory. Moreover, some of the scripts will be rewritten to Python soon and may require some pip packages in future.

Converting Kolla to the Python package with pbr, requirements etc. would make installing dependencies and calling scripts easier. Python scripts could be grouped into modules and registered as console_scripts in setup.cfg. Bash scripts could be registered as scripts in setup.cfg.