minidlna: run as an unprivileged user

- run as an unprivileged user by default
- move generated config to /var/run (/tmp/run in fact)
- disable service until it's configured: there is no way to reliably guess
  where files to be shared are located

Signed-off-by: Maxim Storchak <m.storchak@gmail.com>

multimedia/minidlna/files/minidlna.config

@@ -1,10 +1,11 @@
 config minidlna config
-	option 'enabled' '1'
+	option 'enabled' '0'
+	option user 'minidlna'
 	option port '8200'
 	option interface 'br-lan'
 	option friendly_name 'OpenWrt DLNA Server'
 	option db_dir '/var/run/minidlna'
-	option log_dir '/var/log'
+	option log_dir '/var/log/minidlna'
 	option inotify '1'
 	option enable_tivo '0'
 	option wide_links '0'