Built-in support for Transform

[alt-romes]

We should allow Transform to be used as a property binding value, just like we allow Mat4.
This likely means using the new type-class which is not Syntactic (see #3) and making Transform compatible with M 4 4 in the Compatible families.

I wonder if it would also be possible for user-defined types to extend the compatible type family -- even though Transform should be built in.