Add support for /etc/hans.conf configuration directives

[randolf]

Motivation: HANS is a fantastic solution, and having directives in /etc/hans.conf makes it more convenient when administering multiple Linux servers.

I added support for reading configuration directives from /etc/hans.conf by default (if it exists), and also added a -F command-line argument to support reading configuration files on-the-fly.

I also created an /etc/hans.conf configuration file, which documents all the directives using inline comments.

I also updated the version number to 1.2 in /src/main.c and in /CHANGES (along with a few notes about these new features).

Please note that I have not tested compilation for MS-Windows, but I don't expect my changes to fail to compile as I've tried to keep the code simple-and-straightforward. If someone wants to help with this side of things, that would be great.

Thanks!