Effect Maker and Effect Composer cooperation

This ticket contains just ideas how Effect Maker and Effect Composer could be used together. Concrete tickets could be "Allow opening custom QEN files", so own effects could be added into Effect Composer effects list and "Unify QEN format" so features needed by Effect Composer could be added into the file format.

Intro: QQEM contains 2 file formats: QEN (Qt Effect Node) and QEP (Qt Effect Project). First one describes an individual effect(node) while the second one collects multiple effectnodes into a full effect. QQEM projects are saved as QEP while individual effect nodes are exported as QEN. All built-in QQEM effects have been made with QQEM itself and users can create their own custom nodes collections. Effect Composer uses also QEP and QEN files, although there might be some adjustments.

Case 1: Effect customization: When designer is creating an effect with Effect Composer she notices that effect doesn't behave exactly as she would want or effect is missing some adjustable property.

1) Designer explains the required change to developer.
2) Developer uses QQEM to modify existing effect shader and/or adds the required property.
3) Developer exports QEN file from QQEM and provides that to designer.
4) Designer opens the QEN with Effect Composer and enjoys the enhanced effect.

Case 2: Custom effect: Designer wants a new "Rainbow" effect which is not available in Effect Composer.

1) Designer explains the "Rainbow" effect to developer and which properties she wants to be able to adjust. Possibly also provides images or maybe even link to shadertoy example which looks similar to what's wanted (https://www.shadertoy.com/view/XtBXW3).
2) Developer implements the effect with QQEM.
3) Developer exports QEN file from QQEM and provides that to designer.
4) Designer opens the QEN with Effect Composer and enjoys the new effect.