Discourage changing the number of DoFs / joints for controller after those are initialized?

[destogl]

Discussing parameters handling with @tylerjw and @pac48 it seems that resetting the number of DoF in on_configure in some controllers only complicates the management of those. This does not make much sense because if one needs to change the number of DoF in a controller, another instance of the controller should be used.

Recommended resolution for all (standard) controller in this package:

1. Read the number of joints/joint_names parameters in the on_init method.
2. Remove updates of parameters from on_configure method.

[AndyZe]

This will also improve realtime performance. If you look at the JTC, all of the dynamic memory allocation occurs because it is possible for dof to change size. (Noted in #393)

[bmagyar]

There should be a whole bunch of parameters I'd discourage people from changing, including DOF