Basic logging of issues in certificates.

Added reporting some of issues with certificates (around line 451 in monitor.py is readable list of everything I'm looking for). Currently it only prints out list of problems in each certificate and then stats (how many certificates have given error).
I'll add some tests soon, I just want to make sure that code looks reasonable before I write them.
That's actually OK if this is not an end-entity certificate. The interesting certificates in this case are ones that have  CA:True AND either a SAN extension or a valid domain name in the CN field.