Allow passing points with known Elo values

[kiudee]

Description

The tuner allows the user to pass points to evaluate, which helps to bias the tuner towards particular regions (for example the current default parameters. Often times an engine is tuned against itself and the default parameters are indeed part of the parameter space. In such cases the user knows that the Elo for the default parameters is exactly 0. It would be useful, if it was possible to pass points with known Elo values to the tuner.

Of course, it should be communicated clearly to the user that they need to be absolutely certain that the Elo value is correct. Otherwise, it could have a detrimental effect on convergence to the optimum. For example, an Elo value obtained when using another book is not compatible.

[ChrisWhittington]

This would be very useful