Resolves #343 GUI and Frame Refactor

Major rewrite of the GUI into a module and view form, also using a new Feed class. The frame and frameset data structures have also been rewritten to support memory pooling and response frames.

applications/gui2/src/modules/addsource.cpp

@@ -13,6 +13,8 @@ void AddCtrl::init() {
 }
 
 void AddCtrl::show() {
+	// Note: By chance, the pointer can in fact pass this test as another
+	// widget gets allocated to the exact same address
 	if (!window || screen->childIndex(window) == -1) {
 		window = new ftl::gui2::AddSourceWindow(screen, this);
 	}