check username and UID right on all chainlinks...
security bugfix: assert uid<->name mapping

here's the current setup.  The server establishes the mapping in the first
lookup, and then it's iced into place. We check that all tracking statements
and all signed signature by the user keep the uid<->name mapping, and if not,
then it's a fatal-ish error.

in other words, the mapping should never change, and we start now
to enforce that...
Another attempt at #48

This one with a deeper change
a checkpoint
a non-compiling checkpoint
things are basicaly working...

more testing needed
fix lazy-open race condition
more locking
some cleanups
fix debug prints
Close #50
Close #51
nicer code
privateKey...

still mulling this over..
start work on #46
hacking on #46
more progress on GPG client access
progress on writing an import to pgp function, with full piping
change export -> import

also, split out GPG code so that we can do stuff other than key import
maybe a secret key type?