* this option still checks if the node is busy
* I also improved ssh error handling
* I also added -s, -c, -n, -q, --ssh-keys, -h options

- handle cleanly the case of uva/uvb that is not yet on the reference api
- handle cleanly the case of ceph at rennes
- cleaned up variable names
- removed unneeded stuffs
- simplified file managment
- link between git repository with an environement variable
- rakefile

This reverts commit a577af13.

Discussed with Hyacinthe.