Core of ChessX rewritten from scratch

ChessX is about to be deeply changed. The plan is to separate completely the core functionalities and the graphical user interface. The core part will be rewritten using Qt and SQLite. Most of the data will be kept internally as SQL tables and exported in SQLite databases. This will result in a more modular code that can also be easily used in other programs. At the same time, all database searches will be more straightforward to implement.