Implemented db40, DAO, save and load functions
added load and save dialog and the possibility to generate playgrounds
from loadDialog
Merge remote-tracking branch 'origin/db4o_database' into db4o_database

Conflicts:
	de.htwg.sa.sudoku/src/de/htwg/sudoku/aview/gui/SudokuFrame.java
added jar for db4o and changed file location for database