Add Markov Chain Stream Evaluator

Now that Streaming Expressions supports Monte Carlo simulations it would be useful to add Markov Chain support (https://en.wikipedia.org/wiki/Markov_chain). This ticket will add support for Markov Chain simulations.

Here is the syntax:

let(state0=array(.3, .4, .3),
    state1=array(.2, .1, .7),
    state2=array(.6, .2, .2),
    states=matrix(state0, state1, state2),
    m=markovChain(states, 0),
    s=sample(m, 500))

The Markov chain is initialized with a matrix who's rows represent the different states of the system. The columns represent the probabilities of changing from one state to another state.

For example if we are in state 1 represented by the array(.2,.1,.7), there is a .7 percent probability that it will transition to state 2.