Onboard 1.4.0

These are the main changes that went into Onboard 1.4.0 compared to Onboard 1.3.0:

  * Tablet-mode: (LP: #1366421)
    - Add detection based on acpid reporting the SW_TABLET_MODE switch
    - Add detection based on hotkey events from XInput
    - Add detection by reading tablet-mode state from a few known sysfs paths
    - Add option to the Auto-show page to auto-show Onboard only in tablet-mode
    - Only run GlobalKeyListener when necessary
    - Add tablet-mode settings to Preferences->Auto-show->Convertibles
  * GNOME Shell:
    - Add edge-drag gesture to show the keyboard in GNOME Shell
    - Add option to gnome-shell-extension-prefs to disable edge-drag
    - Enable auto-show only on first start (LP: #1650810)
    - Fix setup.py to have distutils-extra not open extension dir as a file
    - Stop the legacy icon panel from sliding in and out all the time
    - Add license and copyright header to gschema.xml
    - Fix broken string in prefs.js
    - Fix copyright information in prefs.js
    - Clean up prefs.js
    - Remove debug output
  * Auto-show:
    - Refactor settings_auto_show_dialog.ui into new Auto-show preferences page
    - Improve reliability in Unity Dash by reacting only to crucial events
    - Add D-Bus property AutoShowPaused for convertible devices (LP: #1366421)
    - Allow to block auto-show while external keyboards are connected
    - Don't auto-hide while keys are still pressed.
  * External keyboard detection:
    - Detect keyboards with udev
    - Add new preference subpage Preferences->Auto-show->External Keyboards
    - Allow devices to be ignored; e.g. always connected keyboard
  * onboard-autostart.desktop: (LP #1656779)
    - Rename it to onboard-autostart.desktop.in
    - Add _GenericName, _Comment and Icon keys
    - Make it translatable
  * Move listening for global key presses to new GlobalKeyListener.py file
  * Have separate resize protection preference for floating icon and keyboard
  * Add scale for label popup size to Preferences->Keyboard
  * Switch position of "play sound" and "label popups" in Preferences-Keyboard
  * Add MATE'S ContrastHighInverse to the map of known accessibility themes
  * Replace deprecated GdkScreen.get_monitor_workarea()
  * Delay visibility change via D-Bus until all keys are released (LP: #1648543)
  * Indicate in log when Onboard has been started from the project directory
  * Rename tools/socket.py to tools/xembed_socket.py to avoid name collision
  * Reorganize AtspiStateTracker for saner handling of multiple accessibles
  * Update licensing tool for gnome shell extension
  * Explicitely clean up Applndicator status icon on exit
  * Improve error handling when opening layouts files
  * Work around firefox 50 urlbar losing focus and giving wrong caret position
  * Work around broken transparency with Gtk 3.22 (Lp: #1636252)
  * Work around byobu not reporting trailing spaces
  * Fix -Wstrict-prototypes warning when building C++ extension lm
  * Fix negative keyboard window size when screen says zero size (LP: #1633284)
  * Fix geometry hints for minimum size calculation error on startup
  * Fix startup failure on Arch Linux when libdbus-glib isn't installed
  * Fix signed/unsigned comparison warnings when building in Arch Linux
  * Make sure to hide label popups when the keyboard is hidden
  * Ease adjustment of aspect ratio with more handles when docked and expanded
  * Keep more distance when auto-positioning to the Dash search entry
  * Enable docking by default in onboard-defaults.conf.example
  * Update build instructions in README for Arch and Mageia
  * Improve uninstall instructions in README