+/*! prefs
+ *
+ * Set preferences on a number of tracks.
+ *
+ * The tracks to modify are specified in arguments \fB0_track\fR, \fB1_track\fR
+ * etc. The number sequence must be contiguous and start from 0.
+ *
+ * For each track \fIINDEX\fB_track\fR:
+ * - \fIINDEX\fB_\fIPART\fR is used to set the trackname preference for
+ * that part. (See \fBparts\fR below.)
+ * - \fIINDEX\fB_\fIrandom\fR if present enables random play for this track
+ * or disables it if absent.
+ * - \fIINDEX\fB_\fItags\fR sets the list of tags for this track.
+ * - \fIINDEX\fB_\fIweight\fR sets the weight for this track.
+ *
+ * \fBparts\fR can be set to the track name parts to modify. The default is
+ * "artist album title".
+ *
+ * \fBcontext\fR can be set to the context to modify. The default is
+ * "display".
+ *
+ * If the server detects a preference being set to its default, it removes the
+ * preference, thus keeping the database tidy.
+ */