Decoupling of UI and convolver update logic

[jpcima]

In current state of HR2, the parameter changes cause the convolver to be recomputed in the GUI task and to be submitted to the audio processor.

What problem arises from this? it's an issue when the plugin is run in background without a GUI. (for example, when loaded from Ardour DAW, as @sub26nico has reported) It cannot compute changes of parameters, until the GUI gets launched.

In order to fix this, the convolver update logic must be moved to a working task independent from GUI. When I checked, there was not a trivial way to attack the problem, it needs to reorganize elements of plugin. This is not helped by fact that some elements which participate in convolver updates are deeply tied to logic of the GUI.

To solve it, I have engaged in work to rearrange into a less coupled software design. After completing this, it will be welcome to do another round of testing.