Incompatibility with PTC Creo 9

[traversaro]

This is an important annoucement for anyone using this plugin to export URDFs from creo. Due to an incompatibility between PTC Creo 9 and , that you can find documented in https://it.mathworks.com/matlabcentral/answers/1879607-incompatibility-between-ptc-creo-9-and-simscape-multibody-link#answer_1144727?s_tid=prof_contriblnk , at the moment this script does not work with PTC Creo 9.

As the problem will be probably fixed in a future version of MATLAB, and the script is constrained to use a MATLAB version <= R2017b (see #39), this probably means that this script will never support PTC Creo 9.

fyi @vpunithreddy @gabrielenava @FabioBergonti