Karma plugin

I have written karma plugin to add karma functionality in horta-hell.
@rexim @ForNeVeR @folex might be interested in testing and reviewing.
It's a dummy variable. I don't need it but the signature of this https://github.com/codingteam/horta-hell/blob/master/src/main/scala/ru/org/codingteam/horta/database/PersistentStore.scala#L36 requites Option[Any]