i9e: Introduce i9e_cword_is_option_arg().

i9e: Introduce i9e_cword_is_option_arg().

Call the new function to complete --admissible, --sort and --listing-mode of
the ls subcommand and teach the touch completer to prevent filename completion
if a numerical argument is expected. The grab subcommand of para_audiod
also benefits from the new helper: para_audioc learned to complete the three
different grab modes.

Since --admissible expects a mood or playlist argument, factor out the code
from the select completer which returns the list of all moods and playlists
so that it can be called by the ls completer as well.