* Move Category and Feature classes to src dir
* Move database url String to Properties class
* Extract common lines from DatabaseConnector class to execute() method

* Use BusinessObjectFactory to create instance of class depending on ID
prefix
* Create Category class
* Add WHERE clause to DataBaseControllers SQL

* Introduce super class BusinessObject for Application
* Implement Feature extends BusinessObject
* Modify concept of ID, has type prefix now
* Adjust SQL script

* Implement the Application class
* Implement the DatabaseController, that loads an Application with gived
ID to database