fixing deprecation of call to g_type_class_add_private

fixing deprecation of call to g_type_class_add_private

fixing deprecation of call to g_type_class_add_private

fixing deprecation of call to g_type_class_add_private

fixing deprecation of call to g_type_class_add_private

removing gtk+2 stock icons initialization

and fixed thread entry function signature

this clears the compiler warnings about incompatible function
pointer conversion

void foo(void*) -> void bar(void*,void*)

and making the preference dialog a
tabbed dialog

HBox and VBox are deprecated and has been replaced with GtkBox with
Horizontal or Vertical orientation

now it has the stock close image and it's activated
when burn finishes

using change_state signal to update the statefull
gsimpleaction used to show/hide toolbar and filebrowser
instread of modifying the simple action directly

and moved the add toolbar button function
to utils, that it can be shared between
main window, audio tab and data tab

replaced ExoToolbar with a GTK3 Toolbar

added bit of adjustments to the welcome tab

fixed a conversion error from GstDiscoverer to GstObject
when it inherits from GObject

included the app prefix in the UI,
and now the menubar is operational.

by passing the simple action group forward to the
welcome tap creation.

a bit of rework has been going on to replace GtkActionGroup
with the GActionMap & GActionGroup interface

UI Manager replaced with GtkBuilder
and GtkMenuBar with GMenuModel and GtkMenu

made reading audio header safer

fixed busy cursor