scheduler_msgs: add initial draft of new package
scheduler_msgs: replace action and service definitions with ROS topic messages
scheduler_msgs: define request status similarly to actionlib goal states
scheduler_msgs: refine request status values
scheduler_msgs: add requester priority
scheduler_msgs: set current package version, add change log
Merge pull request #27 from jack-oquin/hydro-devel

scheduler_msgs:  new interface definition package