- Use GSettings to improve preference handling
- A new preferences dialog exposing all preferences in the GUI
- Implement config and GUI preferences for various GtkSourceView properties
  such as:
    * Highlighting the current line
    * Match braces
    * Indentation width control
    * Right margin (long-line margin) column
    * Showing/hiding of line numbers
    * Smart home and end keys
- Improved GUI configurability and state persistence, including:
    * A toolbar for commonly used items
    * Fullscreen support
    * Main menu re-organization
    * Improved editor context menu
    * Improved single-instance multi-window support
    * Remember and synchronize size, position, and state, across windows
      and instances
- Support for building against GTK+ 3
- Various other improvements and bugs fixed