Cert file hashing

[greimers]

I added a function to hash a local certificate file in DER format. This is very useful when you have not deployed your certificate, yet, or just for debugging. Accordingly, I added the DER file for google.co.nz and added a button to the sample GUI.

Also added a bit more debug prints to better see which hash belongs to which certificate.

I also removed a lot of blank lines, because I found it a bit hard on my small screen. Sorry, if that messes with your coding style.

Initially I wanted to see why the hashes from Apple's frameworks are different from the OpenSSL hashes. That's why I added hex-output for debugging and realised that OpenSSL as well as the Security.framework pad the public keys with additional but different bytes. If someone knows why that is, please add it to the readme.