playlists management support and playlist editor screen added

doc/ncmpcpp_keys

@@ -35,6 +35,8 @@
 #
 #key_volume_down = 260 '-'
 #
+#key_toggle_space_mode = 't'
+#
 #key_screen_switcher = 9
 #
 #key_help = '1' 265
@@ -47,6 +49,8 @@
 #
 #key_media_library = '5' 269
 #
+#key_playlist_editor = '6' 270
+#
 #key_stop = 's'
 #
 #key_pause = 'P'
@@ -93,6 +97,8 @@
 #
 #key_deselect_all = 'V'
 #
+#key_add_selected_items = 'A'
+#
 #key_clear = 'c'
 #
 #key_crop = 'C'