Until we discover how to only deploy on specific tags on some branches

This reflects the new branch usage scheme.
master -> code for api-server-v?
develop -> code for api-server-devel. Will be rebased on master from
time to time

This is an attempt at making a .gitlab-ci.yml file that can be shared
between mutiple branches, to ease rebasing between then

In effect, this reverts 684a45fe,
5355d08e, and 0e67749f

This is best implemented at the proxy's level, with for example a
ProxyPassReverse directive with apache 2.4

With this commit, ensure that through ssh tunnels, the live kadploy API
can fetch the ssh keys from the vagrant box so as to be able to start a
deployment for the code under development

The development environment cannot completly demonstrate a deployment
because g5k-api relies on using a hook configured on the kadeploy server
to be notified of changes in deployment status. The hook is hardwired to
the production instance of g5k-api

Depending on the current area of devlepment, it is usefull to use a live
oar DB or a local copy.

Add configuration for both in the configuration file so that switching
from one to the other is simpler

- Handle the mysql -> maria migration
- learn to quote scripts for sed
- Use proper sed command
- Use proper name for mariadb service
- Build .deb for stretch
- Typo corrected
- update dependencies in rake build task
- Require lsb-release to vary build
- work on packaging for stretch
- Teach bump tasks to tag releases
- make git push message clearer
- correct destination of stretch packages
- correct typos and publish to v3

As it is now the default

The changes allow the same database.yml and defaults.yml to be usable
with vagrant or gitlab.inria.fr's docker for running tests

In my tests disabling hostiocache improves provisionning performance

It is only usefull for development, not tests

Stop depending on our own boxes hosted on vagrant.irisa.fr

v3 rails 4.2

Grid5000::repository.find can now return exception

returning nil implies the object was not found
returning an Exception implies something unexpected happened when
looking for the object