Configuration options and cleanup

Renamed common.config to node.config and made it's name/location
configurable so it can be outside the git repository.

Moved all configuration to node.config and did some initial
renaming;

* Renamed CONTROLLER_IP to NODE_ID
* Renamed CONTROLLER_IP to NODE_IP
* Renamed CONTROLLER_CONFIG -> NODE_CONFIG
* Renamed $ETCD_HOST_PORT to $ETCD_CLIENT_PORT
* Renamed $ETCD_LEADER_HOSTNAME $ETCD_STARTUP_PEERS
* Removed $ETCD_DEFAULT_HOST_PORT setting
* Renamed $DOCKER_REPOSITORY_HOSTNAME to $DOCKER_REPOSITORY_HOST
* Unified debug logging from 3 variable to to $VERBOSE_LOGGING
* Replaced $ETCD_STARTUP by check on whether $ETCD_STARTUP_IMAGE is set
* Removed incorrect usage() info
Cleanup and comments