#11 Improve ChessBase import annotations and compatibility

[Richard Wiener]

Adds support for ChessBase board graphics from classic .cba annotations, converting arrows and highlighted squares to standard PGN [%cal] and [%csl] directives at the corresponding moves. Improves ChessBase annotation/NAG handling and compatibility for ChessBase database/archive import, with regression tests for annotation placement and PGN output.

Tested on Windows (MSYS2 UCRT64): Release build and full test suite, 215/215 passed.

Patch attached: scid-chessbase-import.patch (based on 9af4dfbf).