Megabytes have shown to be a bit clumsy in the configuration files, so
simply switch to the more useful Gigabytes unit.

Fixes #39

All projects (and namespaces) should start with an "ATx" prefix, having
a capital "AT" and a lowercase "x".

Since we have more to share between the applications than just the XML
wrappers, this is the location to keep common classes and methods.

Note that this only adds the new class library, it does not yet adjust
the existing service code to use it!

Refers to #21