feat: add fast point-to-scalar multiplication via ecrecover

[StackOverflowExcept1on]

Resolves #18

Explanation of how it works:

• ecrecover(e, v, r, s) works according to the formula $Q = r^{-1} ( sR - eG )$ from SEC-1 v2 section 4.1.6 "Public Key Recovery Operation"
• the formula has some limitations: $v \in [ 27, 28 ], r \ne 0, s \ne 0$
• to calculate $scalar \cdot Point$ need to substitute the following values:
  $e = 0, v = PointYParity + 27, r = PointX, s = r \cdot scalar$
• so the formula will look like this after substitution:
  $Q = r^{-1} sR = r^{-1} \cdot r \cdot scalar \cdot R = \cancel{r^{-1}} \cdot \cancel{r} \cdot scalar \cdot R = scalar \cdot R$
• point $R(x, y)$ has coordinates $(r, y)$, where $y$ is calculated from $x$ (coordinate compression) and $v$ (even/odd $y$ is specified)

[pmerkleplant]

The code looks very good! Thanks for taking the time and following the projects coding style <3

I'll need some time to review the math (crysol is a learning project after all :P) and think about reasonability of the functionality.

[StackOverflowExcept1on]

As for math, Vitalik approves xD! https://ethresear.ch/t/you-can-kinda-abuse-ecrecover-to-do-ecmul-in-secp256k1-today/2384
Also in thread there is dude k06a who is the co-founder of the 1inch network and this is basically a rewrite of his code.

[pmerkleplant]

Finally managed to jump back into this, sorry for taking so long.

Note that I renamed to function to mulToAddress() which, imho, carries more semantic meaning. Added a note to the function doc about the performance increase though.

Many thanks for the great PR!