Extract time instant information from log files

[rladstaetter]

Find a way to extract time instant information from log events.

Ideally, a user can define in an easy way to on which place time information is found in a log event. To keep things easy, assume that the log event always stays on the same place in the log event (this simplification is valid for almost all log files I've seen so far). Of course this approach only works for line based logs, xml logs or json logs for example have another way to be structured, but support for other log files than text/line based is still lacking in LogoRRR anyways.

Having this information, new visualisations are possible. Those will be tracked in other issues.