feature request: improve main toolbar

[guiv42]

I am currently considering a partial redesign of the main toolbar. The objective is to provide a significantly visible improvement for a future 2.0 version.
To all users: if you have suggestions for improvement, that's the right moment.

My objectives (don't know if I will succeed):

• integrate completely the player dialog in the main toolbar, and delete the dialog. Almost all controls present in this dialog are already accessible in the main toolbar.
  To add in toolbar:
  • metronome button
  • currently playing tempo
  • numeric display, with a timestamp instead of current midi tick counter
• enable display/hide fretboard and instruments in one single click (replace drop-down menu by buttons)
• make content of toolbar more configurable (e.g. possibility to display/hide some sections)

This is what it could look like (Breeze skin):