Rename host' to 'vhost' in order to make the API more consistent
Add functionality to forcefully expire all sessions in a webapp
Flatten directory structure and unify Error handling
Implement preliminary clustering support

- rename session_summary to find_managers
- add objectName to every MBean if it is not there
- change keys reported from list_webapps to match webapp context name
- add new TomcatCluster class to drive clusters