ocioview: MatrixTransform input parameter persistence

[michdolan]

When editing a MatrixTransform in ocioview, you have the option of using a number of matrix constructors (fit, sat, scale, view). These take simplified input parameters and populate the transform's matrix and offset arrays. The problem is that there is currently no persistence for the chosen input method. The constructors work for initial entry, but reloading the transform from the config loses the input parameters.

MatrixTransform supports storage of FormatMetadata, which is primarily used when transforms are created from reading a CLF/CTF file. An element could be added to the transform's metadata to store ocioview data including Matrix parameters. This would also allow use of new transform constructors, such as using colour-science data to easily populate matrices with color primary or chromatic adaptation transforms.