allow for 'ReportByCpu false' and 'ValuesPercentage false'
this will allow for aggregating total cpu values while keeping derives
(ticks)

Change-Id: Ic22a1b52a5897c18398fa25095a0f3ebcc403ee1
indentation

Change-Id: I0201ac6e3c6e3c9bfcf55b74df6f13b9d961a90e
add example systemd service file

Making use of systemd socket notification feature added in ff270e6d5.
amend comments in upstart config file + disable "console log"

Hopefully avoid some confusion for RHEL6 users which have an old upstart
version.
collectd(1): mention upstart & systemd support
Let snmp_synch_response deal with PDU freeing

When reading from tables, upon errors the PDUs sent are already
freed by snmp_synch_response since they are right after
snmp_send is called.

This commit syncs collectd's approach with other occurences of
snmp_synch_response calls.

There might be a few corner cases where we leak PDUs, but it
is unclear how to check for those since we would need to
have an indication that snmp_send was never called, which
as far as I can tell is not possible.

The potential for failure in snmp_send is rather low and will
be easily spotted though, since when crafting invalid PDUs
snmp send will constantly fail and since valid configurations
can never leak memory.

This fixes #804
Merge pull request #802 from ccin2p3/faxm0dem/cpu-ticks-percentage

allow for 'ReportByCpu false' and 'ValuesPercentage false'
Merge pull request #814 from mfournier/upstart-systemd-examples

upstart and systemd doc & examples
Avoid reintroducing #610, updates the fix to #804

We might as well mess with avoid freeing the req pointer
only when failures occur, otherwise perform as before