Introduce LFIDBearer, a Class for menu bearing UI that offers IDs to menus

Move menu code from scroll list into there
Separate out interface for getting IDs

No longer bother with the focus manager, for menus where not necessary,
this ensures that if focus suddenly changes, it won't break menu UX flow.

Clean up all the static functions by using new static class functions

indra/llui/CMakeLists.txt

@@ -24,6 +24,7 @@ include_directories(
     )
 
 set(llui_SOURCE_FILES
+    lfidbearer.cpp
     llaccordionctrl.cpp
     llaccordionctrltab.cpp
     llalertdialog.cpp
@@ -101,6 +102,7 @@ set(llui_HEADER_FILES
     CMakeLists.txt
 
     ailist.h
+    lfidbearer.h
     llaccordionctrl.h
     llaccordionctrltab.h
     llalertdialog.h