Ginga v2.7.0

• Fix for gtk 4.0 (use "gtk3" backend, it works for 4.0)

• Fix for broken polygon containment test

• Addition of configurable zoom handlers for pan gestures

• Fix for some broken tests under python 2.7

• Update to mode handling via keyboard shortcuts

  • addition of a new "meta" mode used primarily for mode switching
  • most modes now initiated from meta mode, which frees up keys
    for other uses
  • see Ginga quick reference for details on how the new bindings work

• Efficiency update for Thumbs plugin when many thumbs are present

• Default for the save_layout option is now True, so the reference
  viewer will write out its layout state on exit and restore it on
  startup. See documentation in the "customization" section of the
  manual.

• Plugins can now be organized by category and these categories are
  used to construct a hierarchical Operations menu

• Zoom and Header plugins are now not started by default

• Fix for "sortable" checkbox behavior on Header plugin

• Default keyboard mode type is now 'locked' (prev 'oneshot')

• Fixes for missing CSS file in installation script

• Less confusing behavior for workspace and toolbar arrow buttons