Add --multipv flag to run analyzer in multipv 2

[al75an]

Hi,
thank you very much for your time and effort

Could you please add the option to run the pgn-err-stats in multipv 2, 3 or 4
Support interrupt/resume.

Read the output file and save the game headers that are already there.
If the game that is about to be analyzed is already in the output saved headers then skip the analysis.
Save analysis and use the analysis if applicable on the position.

For all analyzed positions save the score, depth, and engine name that analyzes the position in a file.
Add --save-analysis flag to activate this feature.
If the position is already in the database, update the database if engine name is the same and current depth is deeper than what is in the database.
For every positions to be analyzed, check it in database, if it is there then just return the score.
Add --use-analysis flag to activate this feature.