state2proxy

[nikita-0209]

1. state2proxy can be either state2oracle or state2obs. Input arg of state2oracle is a list of states, and that for state2obs is a single state. To use both of them interchangeably as state2proxy, the input form should be the same.
2. Need to add support for transformer-friendly data transformation. This would be as simple as changing the data type of state to int orNone transformation. (In the latter case, transformation to int can be done within the forward call of the transformer itself.) state2oracle cannot be used as the transformer-friendly transformation because: a. for e.g., for the grid if we use state2proxy = state2oracle, input states to the transformer would be [-1, -1] (oracle-friendly) instead of [0, 0]) and the embedding for negative indices is not defined, b. it is not necessary that the oracle takes indices as input (necessary for the embedding layer)