Autoloading: config class

This commit adds composer support to the project. Right now, it's mostly about its autoloader. In future commits, external libs will also be moved to composer.
Additionally, this is the first of a couple of pushes which gets rid of static includes of the class files and instead has them autoloaded. For now, only config.class.php is moved to the new system.
Last but not least, the file now adheres to PSR-1/2 coding conventions (mostly). Documentation is still lacking.