factorize vm_ip extraction

ip extraction is required from a few locations already
refactor ssh-key wiping, add keyscan learning
add scp to iaas module
Merge branch 'config'

This is required for the script feature

Conflicts:
	gandi/cli/commands/vm.py
	gandi/cli/modules/iaas.py
add --script option for virtual machine creation

When using --script, upload script to vm (static /var/tmp/ location)
and run it, instead of spawning an ssh session.
add documentation for ssh extra args parsing
fix merge/commit mixup breaking ssh
Test sshd connectivity to VM before trying to ssh

Replace the actual sleep delay with a real connectivity test
add documentation for the --script create option
use vm_ip in the console method
Merge pull request #50 from kalou/initscript

Add new parameter --script to `gandi vm create` command