Refactor peer-to-peer certificate exchange

This PR goes hand-in-hand with another on the PZH Web Server.  Both or neither must be accepted.

This particular pull request does the following:

(1) Does not create new PZHs unless explicitly requested
(2) Provides an interface for querying whether a particular PZH exists
(3) Turns off CRL checking, as it appears to be broken 
(4) Tidies up a few other function signatures

The big feature added in the other pull request (and that this supports) is the use of passportjs for all authentication.  

http://jira.webinos.org/browse/WP-955

Jira issue: WP-955