* Play in a background process.
* Implement sample rate changing
* Add an ability to process external sound files using created object
* Maybe better interface (with pictograms?) for extra functions (presets save and load, file saving/loading)
  I'll return to this later, when there will be more buttons.
* Hmmm, GtkGLArea seems buggy... and completely dead. So moving to GtkGLExt is nesseccary.