introduced: connection specific properties + property: instanceId

should be solution for #253.

Please note, this brings API breaking changes, namely:

* output log format has been extended with `|instanceId|` value
* P6LogQuery public API changed, P6OptionsRepository (class) -> OptionsRepository (interface)

So my suggestion would be to go for 2.2.0 version, once this goes upstream.

I guess, I'll introduce `migration.md` to sumarize breaking changes across versions.

One thing is probably still open here. `instanceId` propagation for the `*DataSource` classes. As it works for JDBC URLs only right now.

Anyway, the concept of url specific properties requires implementation to be provided per property => we can migrate later those, that would make sence. Still, `instanceId` should provide concept here.

@quintonm comments/objections?
I suppose instanceId should be added to the docs here