Also parse ~/.elasticluster/config.d/*.conf if it exists, for more clusters.
OpenStack provider now *override* configuration options for `username`, `password` and `project_name` if a corresponding environment variable is defined.
This allow you to define fake values for, e.g. `password` and avoid putting sensible data in the config file.
Fixes issue #122 "elasticluster checks SSH key even if it's
password-protected"

If private key is protected by a password, do not check if the
fingerprint of the keypair matches, since paramiko RSAKey/DSAKey
classes only gets you the fingerprint from a pair public/private key.

(well, this I should check more carefully, but for the time being it's fine)
Ugly fix to allow overriding option `ssh_to` for a cluster which is already started
Update ansible playbooks
Squashed 'elasticluster/providers/ansible-playbooks/' changes from 15493d4..f4141ea

f4141ea cosmetic changes
34137b7 Remove `blacs-openmpi` package which is not available on CentOS 6 (apparently)
37770c9 Add support for SLURM on CentOS 6 (Needs to download and compile slurm)
98af8db update `nfsexport` module: add option `state` to ensure the filesystem is mounted _and_ exported
a002181 Fix typo
4a3feb9 If hadoop_tar_url variable is defined, an installation will be performed using a tar file downloaded from {{hadoop_tar_url}} instead of using the deb files defined in `deburl` or `rpmurl`.

git-subtree-dir: elasticluster/providers/ansible-playbooks
git-subtree-split: f4141ea705461e1eb2ab6fc3cbe037e59f309ab7
Add new command `gc3-config` to create a configuration file for gc3pie
Bugfixing
Add support for sge clusters.
Merge commit '4f2dafcc8152ad7883e20f2f1f722c8e6911ad85'
Squashed 'elasticluster/providers/ansible-playbooks/' changes from f4141ea..e6e9837

e6e9837 Fix gridengine on CentOS: error while trying to export a directory *before* nfs server was installed.

git-subtree-dir: elasticluster/providers/ansible-playbooks
git-subtree-split: e6e983795dcbc5e7cbd4cea2d59659a467681355
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