minor cleanup
Provide some tracing to see what's going on.
Ignore more link types
Fix deadlock in sql backend

The connection pool is already thread-safe; it doesn't need
a lock (and will deadlock,du to condition wait)
Work on parallel for-each in scheme
Bug-fix: don't create counters when count is zero
compute-mi: another divide-by-zero bug.
SimpleTrutValue's don't have a count.
Attempt to speed-up scheme ...

by storing Handles directly.  The goal is to have all atom pointers
resolved by the time that th handles get used.
Fix subtle incoming set bug.
Fix subtle handle compare bug.
This is the bug fix, not the last one.

The previous commit was probably healthy to to, but this is the one
that fixes the actual bug. Aiiieee.
iMinor tweaks to avoid excess copying.
Change incoming set to vector
Convert IncomingSet to HandleSeq

It's faster, avoids copying, since we only ever back_insert and
iterate, never delete nor random access.
Try to regain some performance

... by boiling the ocean.  This gave me  a big headache.
Basically, try to avoid excess handle copies.
Use the parallel for-loop

... now that it actually does something.
Fix build breaks lft over from the previous round
Misc minor cleanup
Add extensive documentation