i.e., instead of holding them as Name objects, hold them as serialized
opaque data generated by the corresponding LabelSequence, following the
node structure.  the size of the storage for the labels data is encoded
as part of node "flags".

insert/find now internally uses LabelSequence, and compare() can now return
NONE.  It requires some adjustments to other part of the code and tests, but
they should be generally straightforward.

in tests, note especially that we now have a separeate "." level.  that's
the main reason for the big change to dumpTree().