HSEARCH-968 Indexing Dates and Calendar instances numerically

Introducing a new option to @DateBridge and @CalendarBridge to determine encoding type
True, true. I was about to bring this up on the Jiras as well. Really, it is easy enough to do yourself - once off or via a own helper. But maybe a provided helper might be a good thing. In this context I wonder though, whether we really should expose the Lucene `DateTools` or whether we should create our own. I am tempted to vote for the latter. New issue!?