Replace deprecated GtkActionEntry with XfceGtkActionEntry

Submitted by Alexander Schwinn `@alexxcons`

Assigned to Xfce Bug Triage

This includes removal of GtkUIManager and GtkAction.

All ui.xml files will be removed
Most actions were moved to thunar-launcher and/or thunar-window
Menus will be created on click now (changing menus whenever the selected files change has several downsides)

WIP branch: https://github.com/alexxcons/thunar/tree/ReplaceGtkAction2 (As well includes full context menu on pathbar , which will be part of Bug #14410 )

Pending things to do:

Tasks:

finish check for mem-leaks.
re-write git history in a meaningful way. Try to keep thunar runable on each commit
open code review, explain decisions

Known Bugs:

When right click a folder in bulk renamer: (thunar:5481): thunar-CRITICAL **: 21:19:53.015: thunar_window_has_shortcut_sidepane: assertion '(((extension ({ GTypeInstance __inst = (GTypeInstance) ((window)); GType __t = ((thunar_window_get_type ())); gboolean __r; if (!__inst) __r = (0); else if (__inst->g_class && __inst->g_class->g_type == __t) __r = (!(0)); else __r = g_type_check_instance_is_a (__inst, __t); __r; }))))' failed Traceback (most recent call last):

This change will as well fix the following bugs: Bug #10678, Bug #16256