several tree-settings should be made tree-type or tree-view dependent

[westram]

Separate all -setting into 3 types:

• general (=status quo),
• view-specific and
• treetype-specific

Specifically change:

• scaling factors (vertical distance, group scalings) ⇒ view-specific
• setting for group-counters (introduced with #118) ⇒ type-specific
• Text zoom/pad (there are already two separate settings for radial and dendro/irs) ⇒ type-specific
  • merge both options(?)

Instead of introducing a big amount of new GUI stuff:

• add a separate 'Tree Settings' window for each ARB_NT-window (ie. for each canvas)
• when -type changes → map -type-specific awars to the awars actually used in -settings GUI
• show marker in window-title (sth like '(1)', '(2)'.. as done for main window)
  • move all view-specific options into separate section
• add type-specific section at bottom of settings window
  • group all type-specific settings there
  • show current -type as headline of that section (to make clear stuff is type-dependent)
• add toggles in front of view- and type-specific options (if checked ⇒ option gets "general")

Unclear: how to handle managed configs? perform a -type specific save?

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requires: #727
related: #720