Behavior tree for mission execution and BtNavigator (#227)

* Enable behavior trees and work on cancel capability
* Checkpoint working cancel with traces
* ExecuteMission behavior tree working w/ cancel
* A little clean-up
* Address cpplint and uncrustify issues
* Parameterize the loop rate for the behavior tree classes
* Build a parallel behavior tree for the NavToPose task
* Update the BT Navigator behavior tree to compute a path first before starting the parallel nodes
* Resolve how to handle BTpp dependency; Closes: #51
* Rebase to origin/master
* Inital port to new, updated repo for the behavior tree library
* Can't use shared_from_this in constructor; fix several linter issues
* Start on dynamically creating the behavior tree from an XML description
* Move a few files after rebasing
* Don't have to explicity specify dl dependency
* Working on execute mission BT
* Adapt the BtActionNode class to enable it to by dynamically created
* Checkpoint working version
* Another checkpoint for working version
* Clean up
* Enable the BtNavigator with the new behavior tree library
* Start hooking up params
* Adapt to new Behavior Tree library
* Pass position and orientation when using pose via rviz
* Missed a new file
* Re-enable getting pose from robot; was commented out for debugging
* Revert one of my changes for the BehaviorTree.CPP library now that it is fixed
* Back out the workaround for visibility warning now that it is fixed in the upstream library
* Rebase and cpplint/uncrustify
* Get rid of hardcoded starting position in compute_path_to_pose_action and address some linter issues
* Make the intent clearer for a couple variables names
* Fix a couple inconsistencies with the last checkin