Toolbox Plugins, Fast Fourier Transforms and revamped CSV import

This is another pretty big update!

It will break ABI/API compatibility with other 3rd party plugins, therefore you will need to recompile them. But I promise it is worth it!

This versions introduces a new family of plugins, called "Toolbox", that allows the integration of a Widgets into the app. These widget can analyze, preview and transform data.

Version 3.3.0 contains two toolboxes:

• Fast Fourier Transforms, sponsored by https://www.dji.com/
• Quaternion to Roll Pitch Yaw.

The CSV Importer plugin has been considerably improved, too.