Release v0.9.4

• Implement File -> Revert
• Discovered a bug in the BiDi algorithm we use, which triggered an assert.
  Disabled the assert so we can at least see the result of the bug.
  Workaround: disable BiDi processing. See #35.
• Hide the compile output panel by default, but show visual feedback
  in the font list when a compile warning or error was issued, and show
  the compile output pane automatically when a font item is selected
  that has a warning or error.
• Fixed issue with dragging multiple fonts: the selection was reset to
  a single item, making it impossible to drag multiple fonts.
• Fixed issue where you couldn't select glyphs by clicking outside the
  glyphs.
• Make app icon work better at small sizes.