Bugfixes, HA Support & Output Improvement

Bugfixes:
- The program is now checking, if a node is having the "crowbar"
role. If so, the node will stay online after executing the script.
- HA will be now supported

Minor changes:
- Output improving with colors for a better overview.
- Added a main shutdown script (shutdown.sh)
The opposite of `-z` is `-n`, but actually this is the right way to do it:

    if crowbar machines show $node roles | grep -q crowbar; then