Add worker to send emails depending on information found in transferred system log data

[cliffparnitzky]

With ContaoMonitoring/monitoring-client/issues/7 a sensor should be available, that transfers the system log data. This data should be parsed and depending on configuration an email should be send. This offers the possibility to inform somebody, of errors occurs in the system log of a monitored entry.

We need:

• configuration for each monitored entry to define the action, e.g.
  
• a special email type for the notification center

[cliffparnitzky]

Depends on ContaoMonitoring/monitoring-client/issues/7