Merge branches 'hydro-devel' and 'dont-crash-non-chains' of https://github.com/ros-planning/moveit_core into hydro-devel
Better enforce is_valid as a flag that indicated proper configuration has been completed, added comments and warning
Fix joint variable location segfault
Merge pull request #151 from davetcoleman/constraint_samplers_improvement

Constraint samplers bug fix and improvements