Add trac_ik to IK_SOLVER options

[SDBonhof]

I changed the IK solver to trac_ik locally, but then noticed that you have an option between kdl and trac_ik for the tiago_moveit_config package using optenv, so I recreated that for the tiago dual.

[c-salmi]

In addition to @SDBonhof changes I added a virtual planar world_joint in the srdf empy template (and all generated srdf files from this template).

The virtual joint will make sure the default planning frame of the moveit planning scene is set to /map. This is especially useful/required when using the octomap functionality. Originally the generated octomap was fixed to the /base_footprint of TIAGo, which causes issue when the base moves, since the generated occupancy map moves with it. Including the virtual joint make sure the occupancy map is fixed in the /map frame.