Config properties

Remove the use of default.properties in favor of using a static class, ```ConfigProperties```, like we did in Candlepin. This allows defining things as constants and letting the compiler deal with typos. Also added the ability for Gutterball to read ```/etc/gutterball/gutterball.conf```. We still need to add the auto generation stuff from Candlepin but at least you can override things now. 

This commit updates things in both common and gutterball. I added a test for the ContextListener but the initialized portion had to be ignored at the moment.
Cleaner :+1: