Convert models with material scripts

[osrf-migration]

Original report (archived issue) by Nate Koenig (Bitbucket: Nathan Koenig).

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Summary

Models that contain <script> tags currently do not work with Ogre1, and may never work with ogre2. For example see https://app.ignitionrobotics.org/openrobotics/fuel/models/Textured%20Shapes

Motivation

It would be nice to support automatic conversion of old scripts to new scripts. Not sure if this is feasible.

[azeey]

The current plan is to incorporate the Material parser from https://github.com/osrf/gzweb/blob/master/gzbridge/OgreMaterialParser.cc into gz-sim to parse the default gazebo.material script so that material names for solid colors, such as Gazebo/Red can be supported. i.e, The first step would be to parse diffuse, ambient, emisive, and specular values from the material script. In the future, we might add support for textures and .material script files provided by users.

Note that The gazebo.material script will have to be installed with gz-sim.

cc @iche033