Cut moves before

[mliebelt]

See #46 which was closed, so this is the left over part of it.

Goal:

• Allow to use complete PGN notation.
• Define the start move of the game shown (see #46).
• Hide the moves before that move.

[mliebelt]

The main reason to do this is the following:

• You want to be able to publish something on the internet (like our club chess web site).
• You don't want to show everything to that game, only the fun part of it (nice mate, combination, whatever).
• You don't want to show your opening repertoire to your future opponents.

When you publish now with the implementation done in #46, the whole PGN is included. So how would you handle it:

1. Take the PGN from somewhere.
2. Paste it to the configuration builder, in pgnEdit mode.
3. Cut the moves before (which will give you a FEN and pgnString that fit together).

Of course, all this can be done by hand, but it is error prone.