* Restrict to 80-columns and other style cleanups.
* Make pathfinding a free function and hide the class Pathfinder.
* Split off unrelated utility functions into separate files.
* 5e7c527 Revert "Fix account_lines, account_offers and book_offers result (RIPD-682):"
* b3417ca Revert "Fix pathfinding with multiple issuers for one currency (RIPD-618)."
* 00db7f5 Revert "Clean up Pathfinder."
* Allow pathfinding requests where the starting currency may have
multiple issuers.
* Cache paths over all issuers to avoid repeating work.
* Clear the ledger checkpoint in one retry case.
* Add an additional node at the front of paths when the starting issuer
is not the source account.
* Restrict to 80-columns and other style cleanups.
* Make pathfinding a free function and hide the class Pathfinder.
* Split off unrelated utility functions into separate files.
