v1.9.0-beta2

Prettification, part deux

New features since v1.8.0, including those in v1.9.0-beta1:

• Non-rectangular tags
• Non-rectangular borders
• Left or right-aligned tags, depending on position
• Leader lines attach to closest corner of tag
• Selected tag has a slightly brighter background
• Squawk errors have an error background (red, or orange if also
  selected)
• Leader lines and target symbols have an appropriate brightness
• Target symbols more closesly resemble IRL in shape, though perhaps not
  in size yet
• Add optional top menubar downshift for topsky users, see https://github.com/Epse/vSMR-belux/wiki/TopSky-compatibility

Bugs Squashed:

• ASEL border is not pixel perfect
• ASEL border is rectangular on non-rectangular tags
• Leader lines are too dim