Add initial wotsap file generation tool

Wotsap (http://www.lysator.liu.se/~jc/wotsap/) is a web of trust
statistics and pathfinding tool. It takes a set of preformatted key
data covering the primary UID and signatures on each key.

This commit adds a tool which will generate the file data required for
wotsap. These files still need ar/bzip2 run against them in order to
be fed into wotsap, but are generated from the live keyring data.