Merge pull request #62 from Jailander/hydro-devel

now it is possible to edit the influence zones from rviz
goals are only replaced when the new goal has the same action server name
bug fix
Merge pull request #63 from BFALacerda/hydro-devel

disallowing overwriting of goals is some cases
improving preemption mechanism
Merge pull request #65 from BFALacerda/hydro-devel

improving preemption mechanism
Now action server returns cancelled when the target node is not found on the map