Set version to 0.26.4
Clean up Pathfinder.

* 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.
Fix pathfinding with multiple issuers for one currency (RIPD-618).

* 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.
Fix account_lines, account_offers and book_offers result (RIPD-682):
The RPC account_lines and account_offers commands respond with the correct
ledger info. account_offers, account_lines and book_offers allow admins
unlimited size on the limit param. Specifying a negative value on limit clamps
to the minimum value allowed. Incorrect types for limit are correctly reported
in the result.
Add rfc2616::parse_csv
Make ci_equal a function
Add operator<< for basic_streambuf
Add WrappedSink
Add short_read manual unit test:
This manual unit test explores the outcomes of shutting down
SSL stream connections at various point during a session.
Remove unused RPCServer.
Fix account_lines, account_offers and book_offers result (RIPD-682):
The RPC account_lines and account_offers commands respond with the correct ledger info. account_offers, account_lines and book_offers allow admins unlimited size on the limit param. Specifying a negative value on limit clamps to the minimum value allowed. Incorrect types for limit are correctly reported in the result.
Set version to 0.26.4-sp1
Remove MurmurHash from Beast
Remove sole use of beast::MurmurHash
Remove dead TxQueue code
Make Stoppable unit tests manual
Add missing header needed for boost 1.57 compatibility.
Revert pathfinding changes:
* 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."
Fix account_lines, account_offers and book_offers result (RIPD-682):
The RPC account_lines and account_offers commands respond with the correct ledger info. account_offers, account_lines and book_offers allow admins unlimited size on the limit param. Specifying a negative value on limit clamps to the minimum value allowed. Incorrect types for limit are correctly reported in the result.
Set version to 0.26.4-sp2