LibreCAD v3 GUI Revamp

LibreCAD 3 is the new version of LibreCAD currently under development. LibreCAD 3 uses Lua for GUI initialization, management, plugins and for the various create and modify operations, allowing easy addition of functionality and extensibility through Lua. Lua for GUI initialization and management has a couple of disadvantages like lack of unit tests, compiler checks and more difficulty debugging. Users writing plugins for the GUI require knowledge of the Qt C++ framework. This project aims at shifting the GUI initialization and management to C++ while also providing an alternative API for the GUI for plugins.