Move tolerances to separate header.

- Fetch default tolerances from ros param server in controller.

- Document tolerance-realted functions.
Unit test tolerances-related functionality.
Templatize controller on HW iface & segment types.

- JointTrajectoryController is now a template class that depends on the
  Hardware interface type, as well as on the trajectory segment type. This
  allows to reuse the code across multiple combinations of these two parameters.
  We currently offer plugins for quintic spline segments and position or
  effort hardware interfaces.

- Create a HardwareInterface Adapter class, that converts desired+error states
  from the trajectory sampler (pos, vel, acc) to commands of a given hardware
  interface. Currently implemented adapters for position and effort interfaces.
Better logging messages

- Use NAMED log statements, to differentiate individual controllers.

- More informative info message on controller init: No. of joints, hw interface
  and segment type are reported.
Added ignored manifest.xml files, added rule to .gitignore
Removed manifest.xml from all packages to prevent rosdep heirarchy issues in Groovy and Hydro
Created and documented a script for allowing manifext.xml to be enabled
Add return value to updateTrajectoryCommand method

- Leverage this to discard invalid trajectory messages (eg. too old) and not
  preempt active goals when such invalid messages arrive.
HardwareInterfaceAdapter now also sets commands.
Trivial cosmetic fixes.
Initial controller rostest.

- Currently only exercises topic interface.
Add minimal controller doc.
First version of catkin-spcific scripts. Untested.
Merge pull request #37 from ros-controls/hydro_manifest_removed

manifest.xml hidden in all packages
Log exception string when traj update fails.
Handle singularity at pi when computing wraparound.

- angles::shortest_angular_distance() has a singularity at pi, that can yield
  unexpected results when computing wraparound values. This is now taken into
  account.

- Update unit tests.
Remove unused variable.
Extend controller rostest.

- Pretty much all of the controller code is exercised, except for tolerance
  checking.
Fix bug where goal handle was not being reset.

- When an action goal failed due to path constraint violations, the currently
  active goal was not being reset.
Trivial log message fix.