Add VGC teampreview functionality into environments

[cameronangliss]

I've been sitting on this code for a while but I didn't want to contribute it until I could figure out a minimal implementation, but now I have so here you go! This adds VGC teampreview as part of the MDP, overriding the previous default random action that was taken at teampreview for agents in the environment. The total teampreview, which looks like "/team wxyz" where w, x, y, and z are numbers from 1 to 6, is determined by two doubles orders given by the agent. The first order gives the Pokemon to choose in teampreview that are represented by w and x, and the second order gives y and z.