v2.0

• Added Mode for Multi and Single fixed selection. The Multi selection was already active, but the Single fixed selection mode still not.
• Reviewed method: toggleSelection(int position) - Adapted for Mode functionality. For more details see the comment of the method!
• Added new method getPositionForItem(T item) - Self explanatory
• Added new method contains(T item) - Another useful method
• Reviewed method updateDataSet(String param) - Added the parameter to filter DataSet