Memory overwrite

[RDTm]

The memory is of a fixed length, so when we reach 100000 transistions in memory, we need to start overwriting the first transitions. This is not implemented so far.

Attention should be put to figuring out how to deal with extracting transistions from minibatch once part of the transitions have been overwritten. For example: If we have overwritten transistions till position 10 in memory and minibatch asks for transition nr 11, then the 3 previous "images" in the memory do not correspond to what actually happened before the transition 11. SO we either
1)give a repetition of the 11th image instead of img 10, img9 and img8... as we do in the case when we are asked transistions in the beginng of new game. Downside of it is that actually such transition (same image for 4 frames and then an action) never takes place.
or
2) we forbid the minibatch to ask transitions at that location. Considering we have another 1M of transitions to choose from, frobidding to select 3 of them, seems like no problem.

[RDTm]

seems we ficed it for now