This commit adds more built-in alarms to the Linux formula.

The alerting property can be one of 'disabled', 'enabled' or
'enabled_with_notification'

Currently Syslog doesn't log the priority ('<PRI>').

This is to comply to a comment from @cznewt in
https://github.com/tcpcloud/salt-formula-heka/pull/24.

This patch replaces the "interface" collectd plugin by the "netlink" one. The
"netlink" plugin provides the same metrics as "interface" but plus other
metrics such as the number of dropped packets.

This is now handled by the Heka formula the same way for all the Heka sandbox
decoders. https://github.com/tcpcloud/salt-formula-heka/pull/20

This filter should be configured by the heka formula itself.

The stacklight module dir is /usr/share/lma_collector/common, not
/usr/share/lma_collector_modules. This fixes it.

This fixes the decoder name in meta/heka.yml.

This commit removes the alarm-related filter configuration from meta/heka.yml.
Alarms will be defined in a different way (still under discussion).

This reverts commit 6edb3a7a68.