Allow weighted votes

[danlipert]

For certain use cases, different participants may have different voting weight; i.e. their votes count more or less than other participants. We'd like to implement the input of weighting data for different participant addresses during distribution of the voting tokens, as well as the automatic calculation of voting weights during tallying.

Possibly the easiest way to do this is to issue multiple tokens to each participant according to their weight. However, this may allow users to vote simultaneously for multiple candidates during a voting round. We can therefore split this functionality into 2 modes: one that allows simultaneous voting, and one that disallows simultaneous voting.