Ensure that created use during install command will always be unique.
We assume that the install command must be run to initialize a wallabag instance. NEVER to add more user.
Also, use a better way to retrieve the real name of the database and not the one defined in parameters.yml (which isn't the same for test envi because the dbname isn't defined in parameters.yml but directly in config_test.yml)
Instead of the legacy bin/install here is a symfony command that can initialize wallabag.
There are still work to do on the requirements part (to be sure that wallabag can run like a charm).
I've also added (but commented) the fixtures load part (which will need an extra doctrine package). We'll see that point later.
