Add support for creating provider networks

Implements blueprint neutron-provider-networking

Change-Id: I4bad9483b92875ea5e143b0e11652e01faed35a4
Update readme.md, heat is now enabled by default

Change-Id: Ia36879711aa440f4fba657159afeba2105c6aae4
Merge "Update readme.md, heat is now enabled by default"
Merge "Add support for creating provider networks"
Fix the way Apache site configuration files are used, to improve OS portability

On Ubuntu 14.04, the site configuration file must have a .conf suffix for a2ensite and a2dissite to
recognise it. a2ensite and a2dissite ignore the .conf suffix used as parameter. The default sites'
files are 000-default.conf and default-ssl.conf.

On Ubuntu 12.04, the site configuration file may have any format, as long as it is in
/etc/apache2/sites-available/. a2ensite and a2dissite need the entire file name to work. The default
sites' files are default and default-ssl.

On Fedora, any file in /etc/httpd/conf.d/ whose name ends with .conf is enabled.

On RHEL and CentOS, things should hopefully work as in Fedora.

This change puts all distribution-related site configuration file name differences in lib/apache and
the other services gets the file name for its sites using the new exported function
apache_site_config_for <sitename>.

It also makes Fedora disabled sites use the .conf.disabled suffix instead of removing the .conf from
the file name.

The table below summarizes what should happen on each distribution:
+----------------------+--------------------+--------------------------+--------------------------+
| Distribution         | File name          | Site enabling command    | Site disabling command   |
+----------------------+--------------------+--------------------------+--------------------------+
| Ubuntu 12.04         | site               | a2ensite site            | a2dissite site           |
| Ubuntu 14.04         | site.conf          | a2ensite site            | a2dissite site           |
| Fedora, RHEL, CentOS | site.conf.disabled | mv site.conf{.disabled,} | mv site.conf{,.disabled} |
+----------------------+--------------------+--------------------------+--------------------------+

Change-Id: Ia2ba3cb7caccb6e9b65380f9d51d9d21180b894e
Closes-bug: #1313765