Add FMatrix Type

**Issue by [error454](https://github.com/error454)**
_Wednesday Jul 03, 2019 at 02:48 GMT_
_Originally opened as https://github.com/SkookumScript/SkookumScript-Plugin/issues/6_

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**Is your feature request related to a problem? Please describe.**
Sometimes I really need to use FMatrix and have to jump to C++ to do so.

**Describe the solution you'd like**
Implement FMatrix type and related methods.

No source file, test, entry point, or list of related methods is identified in the issue. Start by locating the plugin's existing matrix types and the C++ FMatrix integration, then define the required type and method scope with the maintainers. Done should include the FMatrix type, its agreed related methods, and coverage for their behavior.

Written by the indexing model from the issue text.