Remote syslog support from OpenELEC settings

This patch remote syslog support by adding two new fields in the OpenELEC settings interface:

 - Remote syslog server (e.g. 192.168.1.13)
 - Log to local disk

The syslog startup script will add the necessary options, and leaves room for a custom syslog.conf from /storage/.config (as it was before). If both are left empty/disabled and there is no /storage/.config/syslog.conf, no syslog daemon is started.

This implements #1861 in the old settings interface.