Add posibility to handle context_menu_request for example for disabling right-click

[simplify-and-focus]

For example for disable right-click, create own method:

METHOD evf_context_menu_request. DATA: ls_func TYPE ui_func, lt_func TYPE ui_functions.

" Inactivate all standard functions
CALL METHOD e_object->get_functions IMPORTING fcodes = DATA(lt_fcodes).

LOOP AT lt_fcodes ASSIGNING FIELD-SYMBOL(<code>).
  ls_func = <code>-fcode.
  APPEND ls_func TO lt_func.
ENDLOOP.
e_object->disable_functions( lt_func ).

ENDMETHOD.

[fidley]

Thanks for contribution!