Improve default UI elements position

[njourdane]

This is the default UI, maximized:

The most important area, the source code, is very small: even the very small line like import cadquery as cq doesn't fit. Also, there are many UI elements, that makes the UI too complex for a new user.

The default UI elements position could be improved.

I suggest something like that:

• main container, vertical split:
  • 75% "workspace" container with horizontal split:
    • 50% code block;
    • 50% rendering block;
  • 25% "information" container with horizontal split:
    • 67% "text" container, with tabs:
      • log viewer
      • console
      • current traceback
    • 33% "inspector container", with tabs:
      • Objects
      • CQ object inspector
      • Variables

Which leads to a lighter and more usable UI: