Complete parseAlgebraicMove

[ejnnr]

There are quite a few things to do to complete the function parseAlgebraicMove in include/ChessGame.php.

• the castling routine is incomplete; it needs to check whether castling is a valid move.
• the function needs better exception handling, e.g. exceptions should be thrown if the move in question is not legal or there is more than one move
• of course the function needs to return something instead of showing test output
• annotation symbols need to be parsed too

EDIT: No. 1-3 are done, only the annotation symbols aren't parsed yet

f04010e also added checking whether there's more than one possible move and throwing an exception if so.