* Added feature to create plugins using VisualizerEditors;
* It's possible to manipulate with GUI content both of GenericEditor's
  plugin component and Visualizer canvas (in the tab or window);
* Created file templates for VisualizerEditor and Visualizer (Canvas);
* VisualizerEditor class minor improvements;
* Other minor improvements;
* Refactoring and stylystic fixes.

* Created 3rd slider-page on creating project steps which is used
  to select appropriate plugin, processor type, plugin GUI template,
  other options.
* Created plugin GUI templates system;
* Created some plugin GUI templates for GenericEditor;
* ButtonGroupManager and TiledButtonGroupManager classes minor
  improvements and fixes;
* Changed index of ProcessorType::UtilityProcessor;
* Other minor bugs fixes.