find way to instantiate brain outside Code

[fabioseel]

Simplest way without affecting the samplefactory library too much would be to write it to disk right after initialization of everything.
For this, it might be easiest to instantiate a Runner, acess a Learner, set the actor_critic weights and save
However, if we heavily modify the library for the Goal system, we might also go and implement proper Brain usage in SF (risk of side effects :o)