New DatabaseReader reads ledger numbers from database.

A start at a database reader - so far only for ledger numbers.
So I've been unable to get this to work.  Do you understand how this operates?

I have it down to this variable here:  https://github.com/rec/rippled/blob/431dd995bc62b00b2a4fe8e168cc9036fe97229f/bin/ripple/ledger/DatabaseReader.py#L40

If I set it to true, I get a long delay and no data.  If I set it to false, it all works??