This moves the official Debian packaging into ring-project. Jenkins
should now be able to run packaging jobs and publish packages. It
should also make it easy to add a `verify` check on Jenkins to test
packaging patches.

This will make it much easier to work on packaging issues because the
build environment is now reproductible on any machine.

The patch adds Makefile targets to create packages such as:
 - package-all
 - package-<DISTRO>

Builds are all done inside Docker containers and it is possible to
build many at a time with the `package-all` target.

To debug a build, use `package-<DISTRO>-interactive` to obtain a shell
inside a container, ready to launch a build.

Tuleap: #781
Change-Id: Id87a74a6c412ffc5bf82b9562639ce5a9424b06a

This new documentation can be built using `make docs`. It should be
built automatically via a hook on github and published on
https://ring.readthedocs.org.

This allows for much better formatting and is more pleasant to browse
for new contributors. It is possible to build the docs using the
Makefile at the root of the repository.

Change-Id: I664d4662b76c525f2a67eac6266bada3e94aa835
Tuleap: #595

Begin merging all helper scripts into one. Support for other distros
is to be added in the future.

Tuleap: #451
Change-Id: I8ab09502a58ce6a6ccf154be2cf51af401759365