cloud_aws: retry attach_eip to tackle allocation ID failure

https://forums.aws.amazon.com/message.jspa?messageID=470512
Merge pull request #31 from lamadon/retry_eip_association

cloud_aws: retry attach_eip to tackle allocation ID failure
cloud_aws: changes to enable deployment of on-spot instances (even with private ip address).
Merge pull request #32 from epankala/spotify

cloud_aws: changes to enable deployment of on-spot instances (even with private ip address)
tool: remove-config command

also changed add-config and remove-config to log each action at the info
level if verbose flag was used, otherwise they're logged at debug level.
GitVersionControl: handle deleted files
Merge pull request #33 from saaros/remove_config

tool: remove-config command
AWS: iops
AWS: Instance volume tagging
Merge pull request #34 from epankala/iops

Iops
libvirt: make hypervisor configurable but only support kvm for now
libvirt: preliminary support for lxc targets and btrfs storage

NOTE: btrfs volumes require a patched libvirt, see
https://www.redhat.com/archives/libvir-list/2013-September/msg00530.html