Flatten feature + minor refactoring

New:

• Flatten feature.
  • Tired of having your midis tempo being all over the place? Tire no more, as now you can fix that without worrying about audible changes! (thought through obscure means)
    • Click on the added MIDI and click on Collect info button.
      Collect info button position

      
    • In the opened window click Copy time map
      Time map copying from info collector

      
    • The midi's settings window will pop up back with updated Time map status (at the bottom). Now you just type in the desired tempo, apply the settings, and off you go with merging/conversion :)
      Do not forget to type in desired tempo

      
  • The order of operations is not quite important though
  • Manual/Wiki update will be made eventually 🐱