Add support for .fig file parsing

[nedtwigg]

MATLAB .fig files are just MAT-files. (Undocumented MATLAB)

When opening one of these files in matfilerw, it errors with incorrect matlab array class: function_handle.

If this is fixed, it will enable DiffPlug to view and diff figure files.

[ennerf]

The function_handle type has the standard header (attributes, dimensions, name) followed by a struct. Reading .fig files will also require adding Segment 2 properties as in #18 to read the function_handle_workspace.

[nedtwigg]

Is this fixed in HebiRobotics/MFL?

[ennerf]

Yes, MFL supports reading .fig files.