Definition of Rust API

[djetchev]

The goal of the issue is to define the abstract API for Alba Telescope in a markdown Design doc. This follows a recent discussion between @rrtoledo and @tolikzinovyev.

The main discussion points:

• Weight function

• Representation of the function from a user perspective

• Handling the lottery (binomial or Poisson distribution)

• Investigate and document the main integration points with Leios/Peras (or Mithril?)

• Vote.hs in the Peras design repository

• functions such as binomialVoteWeighing look generic and they can be reused in other applications of Alba certificates - where should they reside (probably make them part of the Rust repository)? Also, @tolikzinovyev 's work on a Poisson distribution version of this.