Auth logic code.

Start designing way to map auth source to user and setup
testing code.
Missing header
boilerplate code to use visitor pattern w/ auth source and module
minor cleanup
Factor out the code that load a propery tree from xml file
FileAuthSourceMapper can now maps wiegand card.

The FileAuthSourceMapper object is now able to load a config file
and maps wiegand card to user. A small unit test is present.

This mapper is provided by the Auth-File module.