Generate microdescriptors with "a" lines.

Generate and store all supported microdescriptor formats. Generate
votes with one "m" line for each format. Only "m" lines with version
info matching chosen consensus method will be voted upon.

An optimisation would be to combine "m" lines with identical hashes,
i.e. instead of "m 1,2,3 H1" and "m 4,5 H1", say "m 1,2,3,4,5 H1".