Remove LearnCircuitBuildTimeout CircuitBuildTimeout from exercise.sh.

I think I left these in because the host I was running the exercise
script on had an old tor, but they're not needed anymore. Cf.
4f7b24b30abbb8af4cd83bdf171e6f8ea25b18ca.
undo overzealous factoring - enforce v4/v6 behaviour only applies for registration helpers
rename facilitator binaries to have more "unique" names.

facilitator              -> fp-facilitator
facilitator.cgi          -> fp-registrar.cgi
facilitator-email-poller -> fp-registrar-email
facilitator-reg          -> fp-reg-decrypt
facilitator-reg-daemon   -> fp-reg-decryptd