Add basic middle click support (#36)
Add support "action-middle-click-titlebar" dconf key (#36)
Replace xprop to ctypes based solution
Correct onClickTitlebar method usage (#36)
Change attributes

* `htitlemode` doesn't have `legacy` value anymore.

* Add `htitlemethod` attribute.

* Rename `htitle-button-layout` to `htitlebuttonlayout`.

* Remove `hidetitlebarwhenmaximized`.
Drop Fx 24-28 versions support
Reorder and cleanup HTitleTools.jsm
Rename settings.xul to options.xul
Create HTitleWindowControls.js
Fix libs loading
Move prefs observer to HTitleTools
Move pref_page_observer to PrefPageObserver.jsm
Clean up
Usage open() and close() methods for every action
Rename Gdk to Gdk2
Add basic GTK3 support
Merge Gdk3.jsm and Gdk2.jsm to Gdk.jsm
Fix HTitleTools.lowerWindow()
Create HTitleShare.jsm
Rename HTitleTools.jsm to HTitleUtils.jsm