Fixed bugs in ETS2/ETS3 when displaying prismatic joints

[xiaoniaogangsi]

Considering the bugs mentioned in #5, I tried to fix the visualization problems of the prismatic joints in the teach methods of both ETS2 and ETS3. The related file RTBPlot is also modified.

I also added improved handling and validation for prismatic and revolute joint limits in ETS2 and ETS3 teach and plot methods. The teach panel now uses correct joint limits and scaling, and prismatic joint visualization is updated to reflect actual joint values. Correspondingly, RTBPlot is updated to support new teach panel arguments and correct joint scaling.

Whether this change will affect other parts of the toolbox still needs further confirmation.