Add support for EGL for Cairo-Dock Core

EGL will be required for Wayand, but it can also be used as a replacement for GLX. Since 3.3, the OpenGL framework is modular, so we can just add a new OpenGL backend. GLX should remmain the default one though (it has a wider graphic card support).

Add a global color option to the simple config for Cairo-Dock Core

The goal is to be able to change the color of several objects with a single option (in the simple configuration window). For instance, menus, dialogs, dock and labels could share the same options for background color, outline color, and corner radius. Outline color could even be the same as background color, but ful...

New menus look for Cairo-Dock Core

The goal is double: - make the menus more consistent with the rest of the program (especially with dialogs, so both should share the same options about shape and colors) - free ourselves from the tyranny of GTK3 (menus should have icons, at least optionally)

Global menu support for Cairo-Dock Plug-ins

Add support for the global menu. First support the Ubuntu's implementation, that works on Dbus. Make the code so that other implementations can be supported in the future. The applet's icon should give the ability to: - close, minimize, restaure, close the current window - display the menu of the current window in a...