Logs should use syslog syntax

[LotharSee]

Logs are currently using a custom format.

Jul 15 22:01:10 alexandre INFO | dd.collector | collector(dd-agent:137) | Exiting. Bye bye.

Using the syslog syntax would simplify its parsing.

Jul 15 22:05:01 alexandre /USR/SBIN/CRON[21885]: (munin) CMD (if [ -x /usr/bin/munin-cron ]; then /usr/bin/munin-cron; fi)

It is also a first good step if we want to use the full power of syslog (facility, level, ...) #91

http://www.ietf.org/rfc/rfc3164.txt