Add script to migrate host from source to target cloud

Add script scripts/migrate_host.py that reads configuration file
for the hardware environment and uses IPMI protocol to decomission
the host specified as an argument in the command line.
Add description of migrate_host.py script to README
[doc] Fix command format in README and help for hostname param
Improve logging and exception handling
[doc] Add docstring to Fuel class
Add deploy_changes step to main()
Set arguments types
Fix wait_for_node method of Fuel class

Correct conditions for detecting new node and detecting node
status change.
Add script for migrating host to Mirantis OpenStack