Missing descriptions of three vote types listed in index.md

[cottage14]

index.md lists eight voting types, with links to explanations on vote_types.html

vote_types.md only has five explanations, lacking explanations for

• Multiple Non-Transferable Votes
• Candidate or Party voting with preferential trickle-down
• First in Class (N-x-points based voting)

If these voting types are supported, they should be described.

[cottage14]

Added three description areas on vote_types.html, but only found information that I could use to populate one of them.