Search of context hierarchy for voice for lyrics is optional

Search of context hierarchy for voice for lyrics is optional

 - add new context property, searchForVoice, to indicate
   whether the extended search for a voice containing lyric
   rhythms should be conducted

 - fixes 1579

 * lily/lyric-engraver.cc

   test searchForVoice in get_voice_to_lyrics () to decide
   whether to conduct an extended search

 * ly/engraver-init.ly

   set default value of searchForVoice to #f

   (also in passing remove duplicated instrumentname
    and shortInstrumentName settings)

 * scm/define-context-properties.scm

   add and document searchForVoice