added new ik solvers: free_angle, joint limit avoidance (jla), mid_joint. Abstracted solver in plugin to ease using different solvers in plugin
bugFixes to ConstraintGroup/Orientation methods

  - ConstraintGroup: propagate SetIK() to child Constraints
  - ConstraintGroup: size Jacobian as matrix not vector
  - GoalOrientation: use correct ordering of goal-pose in CalcError
sync updates from master
add support for variable-length constraints
add init and updateErr/Jac methods to Constraint
port jla_ik to constraints::AvoidJointLimits
Merge pull request #1 from ros-industrial/constraint_list

Constraint list