khal.conf.sample :  Rewritten: complete, clean, and includes Self-Sign/Corp-PKI CA Cert verify

Aloha,

I've rewritten the sample configuration file.
I found it to be kind of hard to follow before. This new file contains all the information form the old file but in a much cleaner way. It also includes instructions for verifying Self-Signed or Corporate PKI CA Certificates.

First, I define default location for khal.conf
Second, outline the sections of the configuration file
Third, step through each section, section by section & option by option. Explaining each section and option along the way.

There is the sample configuration at the bottom. However, with all comments removed. The comments were removed because everything has already been defined. With them removed the example is much easier to follow.