Update and add better documentation

[Jim Hodapp]

Not being familiar or having much experience with apparmor, I've found it quite frustrating in getting started by reading the documentation that exists. Current issues with the docs that I've found are:

* Out of date documentation on the web found with Google
* Split documentation between Ubuntu-specific and apparmor in general, even though Ubuntu is the upstream maintainer of apparmor.
* Lack of easy to follow and useful tutorials and other getting started material. Current documentation seems geared more towards the advanced user that already mostly knows what they're doing and simply needs a reference.
* http://wiki.apparmor.net/index.php/QuickProfileLanguage doesn't include dbus, signal, ptrace or unix rules

A really useful tutorial would be centered around working with interfaces with snapd. Of course this is not meant for the average user, but there are still plenty of interfaces to be created and such documentation and best practices would be very helpful.