[hector_exploration_planner]
* Add visualization for exploration transform
* Change color of frontier markers depending on if they're valid or not
[hector_exploration_planner]
* Change generation of frontiers
[hector_exploration_planner]
* Fix inner exploration
Merge branch 'experimental'

Conflicts:
	hector_exploration_planner/src/hector_exploration_planner.cpp
Merge branch 'master' into rc_stabilize

Conflicts:
	hector_exploration_planner/src/hector_exploration_planner.cpp