Add test case for model conversion

[aymanhab]

To make sure old models deserialize and display correctly, need a textual rep of Display and a suite of old models using old format.

[jenhicks]

@aymanhab Is this still an open issue (per your OpenSim 4.0 presentation)?

[jenhicks]

Additional comment from @aseth1
Most components are verified by virtue of older model files being used by other test cases. But in many test cases (esp. Joints, Constraints and Forces) models are built programmatically (without loading a model from file) and the serialization loop is tested only in the latest version.

In order to ensure that the content of older models is preserved they must be verified to contain the same content in the latest version of the model.

[aymanhab]

I tried to open the simple model bouncing_block from release 3.3 and it failed to open with
PointToPointSpring::connect() failed to connect ....

[aseth1]

@aymanhab In which build did you try to open the model? Is that model in the repository. Is there a test case for it? What was the complete error message? That will help track it down. Thanks!

[aymanhab]

@aseth1 This is occuring in my build of the GUI based off master before your last commit, so it may have been fixed. The model is from earlier distribution (3.3) and the error message is attached.

[aseth1]

Great. It's helpful to know that the component could not be found. It may be addressed by recent changes but it could also be due to a bug in the update from XML. Can you point me to the model file.
Thanks.

[aymanhab]

Sure, OpenSim3.3\Models\BouncingBlock\bouncing_block.osim Since we split the repositories, the model file doesn't live in the opensim-core repo.

[aseth1]

PointToPointSpring does not override updateFromXMLNode(). We should not spot fix this. Instead we should write a test to find all the Components that should be updated and we know it should find this one.