update bernstein-vazarani problem representation

[wrigjl]

The BV problem description includes a list of function values and a number of bits "n". The latter is unnecessary because it can be inferred from the length of the list which must be a power of 2

$$n = log_2 len(list)$$

Right now, quantumsolver depends on having N readily available, but we should simplify the parsing/representation of this problem AFTER we have the link between Redux and quantumsolver working.

Oh, and while here, rename the "S" variable to "i" to avoid confusion with the secret string that BV produces as its solution.

[wrigjl]

A quick update, quantumsolver now either accepts {nbits: 2, f: [0, 1, 0, 1]} or simply [0, 1, 0, 1] as an input, so once #60 is merged, we can simplify the API between redux and qs.