Only check for IK when needed

[jstnhuang]

The system will check for IK whenever it creates a gripper mesh, coloring it appropriately. This means it checks for IK solutions at unnecessary times:

• When saving a pose (because poses are demonstrated kinesthetically there must be an IK solution)
• When loading a previously recorded action

It's only necessary to solve IK:

• When a pose is edited in rviz
• Prior to executing an action (because the torso height might change)
• When executing and a pose is relative to a landmark

The unnecessary checks do slow down the execution quite a bit, it takes O(# actions) seconds to load an action.