Bug fix

When no item was set in the collection it would throw a notice
Added the autoloader support

Added loaders
- namespace loader, used for PHP namespace autoloading
- prefix loader, used for prefix autoloader, default is the _ char the
prefix. Could be changed with the setPrefix function (only available on
the PrefixLoader)

Added PHPUnit test for the AbstractLoader and LoaderFactory
Merge remote-tracking branch 'origin/master' into DB