new implementation of the database-handling
some adjustments
structured some project-files with packages
deleted dublicate files
added ObjectHandler, a superclass of the User- ShoppingL- and Item-Handlers
removed unnecessary constructors from User, ShoppingL and Item
updated tests. they should now run error-free, but wont cover many testcases
Merge pull request #65 from marcSchneiter/master

new implementation of the database-handling. some tests will be faling for the moment, ill update them till sunday