Improve UI look - menus

[tomcl]

Menus

The main window has electron menus + custom menus.

This is frankly weird. Better:

• The electron menu bar should be removed
• All menus should be purpose-built on the main menu bar
• Menus should be rationalised

Suggested strategy:

1. Add recents and an exit Issie item to project menu
2. Make waveforms button smaller by renaming it waves without >>>. This button will eventually be removed anyway
3. Add two custom buttons for edit and view menus, like project and sheet buttons
4. Sheet menu should be implemented as now. All other menus should be implemented as electron menus (as now), but accessed from custom buttons on the Issie filemenu bar.
   • Not sure how to do this, but believe it is pretty easy, see electron documentation and google
   • Another option is to rewrite custom menu code (including accelerators) to replace electron menus. That is trickier
5. Having done this, we can delete the electron menu buttons and the line they sit on.
6. It might be worth making the menu bar buttons all a bit smaller.