Winboard player construction - simplify

[lrozenblyum]

During implementation of #278 it has become obvious that winboard player creation via static 'factory' method looks out-of-common style. It is also against OOP principles.
We should allow WinboardPlayer creation via poor constructor.

Risks:
a) 'singleton' enforcement won't be as easy (although we don't have it right now)
b) some tests which were depending on our 2-phase construction of the player (with separate initCommander call) may behave differently and not test well what's needed. Requires good investigation.