Replace THIRD_PARTY with machine-readable LICENSE

This converts the THIRD_PARTY.md file into a machine-readable format.  This allows easily parsing the file if necessary.  It also happens to be the same format recommended for debian packaging - in case we ever want to go that route.

The new LICENSE file contains all of the information from the THIRD_PARTY.md file plus some stuff that was missed in the original THIRD_PARTY file.