implement graceful shutdown of bcrypt compute processes.  fix bcrypt.get_rounds (was throwing an exception)

fix regression in keysigner - ensure non-default VAR_PATH is relayed to compute processes - issue #213

remove the deep __heartbeat__ checks performed from browserid (the webhead), while dbwriter should ping the database to ensure health - closes #566

(loadgen) fix console output at startup - properly message # of pre-created users or users to be created via API

(loadgen) add '-l' option to list activites, and '-a' option to specify a list of activites to run (ignoring others).  simplify '-o' so all this stuff uses the same mechanism

more issue #598 - add test and fix for other places where exceptions leak out of JWCrypto and cause 500 errors rather than 200 failure responses.

the verifier is more helpful if you leave off content-type headers, also did you know we support application/json?  closes #643

(loadgen) add -u option that allows one to specify a numeric range which will make load testing with a large database possible - issue #504

(loadgen) implement assertion generation in loadgen client, hook up signup and signin flows - issue #504

(loadgen) now starts up, generates 30 keypairs, adds 30 users - simulated signup mostly updated to new apis - issue #504

repairing load_gen - issue #504 - update pathing, alter fake_verification WSAPI to query the database rather than to use email interception (which no longer works)

initial implementation of request forwarding, cookies set from dbwriter are still not being properly passed through - issue #460

add the dbwriter process.   it's not yet hooked up, but starts up and runs, and included in health check.

reorganize browserid process - break out view serving and wsapi handling.  preparation for dbwriter split.  issue #460