Single Transferable Vote

Add single transferable vote as a new election mode (current mode winner takes it all)

It is a voting system where each voter makes a preference list of the candidates. To select the winner one iteratively removes the one with the least votes and transfers votes to the other candidates according to the ranking made by the voters. Thus, it does the same as Stichwahlen but in a single round of votes. Therefore, it can be fairer in situations where a single candidate cannot reach the 50% mark but is still elected since over all candidates got the biggest amount of votes.

There is a nice explanation video by CGP Grey