Connect via I2CP and ask the router to look up
the lease of a hash, convert it to a Destination and return it.
Obviously this can take a while.
All calls are blocking and return null on failure.
Timeout is 15 seconds.
To do: Add methods that allow specifying the timeout.
As of 0.8.3, standard I2PSessions support lookups,
including multiple lookups in parallel, and overriding
the default timeout.
Using an existing I2PSession is much more efficient and
flexible than using this class.