Add argument `include_config_dirs` to `Configurator.fromConfig` and move lookup of config directories to `Configurator` class
Fix ImportError while building the documentation
Add documentation for `<class>_min_nodes` option
Cosmetic changes
Allow updating some configuration values on an already started cluster by editing the configuration file.
Before this commit, the whole configuration was saved together with the cluster and it was impossible to update some values, for instance `ssh_to` option or `user_key_private`. Now, updating these values in the configuration file will also update the class when this is loaded from disk.
Do not save _cloud_provider and _setup_provider together with the cluster, so that changes in the configuration file will be loaded every time elasticluster is called.
Before this commit, if you mistaken the cloud configuratino you had to *destroy* the cluster and then start it again.
Update configuration
Rename `ClusterRepository` to `PickleRepository`
Also mention OpenStackCloudProvider
Update documentation: add OpenStackCloudProvider API docs.