Handling of tags giving people that contribute to the recording e.g.

Composer, Conductor, Lyricist, Mixer etc. including TIPL and TMCL held as
vector of artist name and role in CMusicInfoTag and CSong. Contributors
are held in library as artists with role in song_artist and role tables determining which tag was source of data.

Remove JoinPhrase and boolFeatured as unused elsewhere, artist string now stored rather than built.

Queries changed to generally access only standard artists not other roles

Contributors included in both JSON and Info Labels

Add example/default role nodes and modified SongInfoDialog so data
visible.

addons/resource.language.en_gb/resources/strings.po

@@ -14113,6 +14113,7 @@ msgstr ""
 
 #. Concert composer of the music (if present)
 #: addons/skin.confluence/720p/DialogPVRRadioRDSInfo.xml
+#: addons/skin.confluence/720p/DialogSongInfo.xml
 msgctxt "#29903"
 msgid "Composer"
 msgstr ""
@@ -14125,6 +14126,7 @@ msgstr ""
 
 #. Conductor of the classic music (if present)
 #: addons/skin.confluence/720p/DialogPVRRadioRDSInfo.xml
+#: addons/skin.confluence/720p/DialogSongInfo.xml
 msgctxt "#29905"
 msgid "Conductor"
 msgstr ""
@@ -18247,3 +18249,57 @@ msgstr ""
 msgctxt "#38032"
 msgid "Angle"
 msgstr ""
+
+#: xbmc/dialogs/GUIDialogSmartPlaylistRule.cpp
+#: xbmc/playlists/SmartPlaylist.cpp
+msgctxt "#38033"
+msgid "Role"
+msgstr ""
+
+#. Orchestra playing on the recording (if present)
+#: addons/skin.confluence/720p/DialogSongInfo.xml
+msgctxt "#38034"
+msgid "Orchestra"
+msgstr ""
+
+#. Lyricist that wrote the lyrics of the song (if present)
+#: addons/skin.confluence/720p/DialogSongInfo.xml
+msgctxt "#38035"
+msgid "Lyricist"
+msgstr ""
+
+#. Remixer of the song (if present)
+#: addons/skin.confluence/720p/DialogSongInfo.xml
+msgctxt "#38036"
+msgid "Remixer"
+msgstr "" 
+
+#. Arranger of the song (if present)
+#: addons/skin.confluence/720p/DialogSongInfo.xml
+msgctxt "#38037"
+msgid "Arranger"
+msgstr "" 
+
+#. Engineer of the song (if present)
+#: addons/skin.confluence/720p/DialogSongInfo.xml
+msgctxt "#38038"
+msgid "Engineer"
+msgstr "" 
+
+#. Producer of the song (if present)
+#: addons/skin.confluence/720p/DialogSongInfo.xml
+msgctxt "#38039"
+msgid "Producer"
+msgstr "" 
+
+#. DJMixer of the song (if present)
+#: addons/skin.confluence/720p/DialogSongInfo.xml
+msgctxt "#38040"
+msgid "DJMixer"
+msgstr "" 
+
+#. Mixer of the song (if present)
+#: addons/skin.confluence/720p/DialogSongInfo.xml
+msgctxt "#38041"
+msgid "Mixer"
+msgstr ""