Install default config files
Merge pull request #66 from po1/install-default-config

Install default config files
Honor unspecified vel/acc in ROS message. Fix #65.
Merge pull request #67 from pal-robotics/issue-65

Honor unspecified vel/acc in ROS message. Fix #65.
Refactor how the currrent trajectory is stored.

- Handle concurrency in the current trajectory between rt and non-rt threads
  using the simpler RealtimeBox instead of the RealtimeBuffer, because our
  usecase does not fit well the non-rt->writes / rt->reads semantics.

- As a consequence we no longer need to store the msg_trajectory member, but
  only the hold_trajectory, which must still be preallocated.
Work tolerance checking methods.

Until now we used the currently active goal handle for performing tolerance
checks. Using the goal handle stored in segments is more robust to unexpected
goal updates by the non-rt thread.
Reorder how time and traj data are updated.

In the update method, fetching the currently executed trajectory should be done
before updating the time data to prevent a potential scenario in which there
is no trajectory defined for the current control cycle.
Merge pull request #69 from pal-robotics/issue-60

Fix issue #60
Action interface rejects empty goals. Fixes #70.
Merge pull request #71 from pal-robotics/issue-70

Action interface rejects empty goals. Fixes #70.
Add missing headers to target files.
Fix class member reorder warning in constructor.
Better logs when dropping traj points. Refs #68.
Default stop_trajectory_duration to zero. Refs #73
Merge pull request #74 from pal-robotics/stop_traj_duration_default

Default stop_trajectory_duration to zero. Refs #73
Merge pull request #72 from pal-robotics/minor-maintenance

Minor maintenance
Link shared libraries to catkin libraries

GCC is quite lenient with missing symbols on shared libraries and
doesn't event output any warning about it.
When building with other compilers, missing symbols result in build
errors.
Merge pull request #75 from pal-robotics/fix-linking

Link controllers to catkin libraries
Added package for diff_drive_controller.
Had to create a modified version of CMakeLists.txt for qt creator to work, will remove later.
Added odom message type + fixed loading problems of plugin.