Charge field

[lubynets]

1. Added charge field for Track. For daughter class Particle it works in the same way as mass field - linked to the PDG code unless user explicitly sets specific value different from table one.
2. In order to avoid a conflict of field names an additional check is implemented - if one tries to add a field with already existing name (both default or user-defined), an error will be thrown.

Note: In some pieces of code based on AnalysisTree (e.g. CbmRoot interface, PFSimple, Pid etc) the charge could be set as a user-defined field. Now it should be fixed, and a default field should be used. Check described in item (2) will help to localize these places.