editor: add editor_shutdown() into header
Dependencies: mainly finished

   Suppose we have pack_end(box, but1)
   1) when I delete pack_end from box, i need alse delete it from dep
   list of but1
   2) when I delete but1, i need to delete this pack_end from box.
   (and from dep list of each widget, if there are several as func
    params)
   3) When change box1 -> box2, need to delete this prop from box1.
Remove checking for GUI_TYPE_OBJECT from entry property editing

 - reload win, when parameter is changed from one object ot another.
reload win, when deleting widget
Remove obj creation from BigBang when added into other sequence
Sequence add: entry in the buttons box instead of new win
Fix if prop is NULL
Delete from Sequences View works now
change active_context to context from widget
fixing gui_widget_init()
fix small mem leak
fix my small bug
typo
gui_widget: change wdg_prop_get() to search in list
gui_widget: remove prop_hash from widget
editor: clean propview, when click on head element
remove propview_list_clear() and use propview_build(NULL) instead
Update Todo
User callback support in GUI
add fields to description section