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.
Set version to 0.26.4-sp1
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
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 bugs in pathfinding with XRP as the source currency
Set version to 0.26.4-sp3
Merge branch 'release' into develop
Construct Server after Overlay and WSDoors:
When the ServerHandler is constructed before the Overlay, an incoming
connection received after the server's listening ports have been opened
but before the Overlay object has been created causes a crash.
Tidy up split_commas function and use it in Server

Conflicts:
	src/ripple/server/impl/ServerHandlerImp.cpp
Accept generic arguments in ci_equal
Clean up CKey and RippleAddress (RIPD-672)

* Remove CKey dependency on RippleAddress
* Create RAII ec_key wrapper that hides EC_KEY and other OpenSSL details
* Move CKey member logic into free functions
* Delete CKey class
* Rename units that are no longer CKey-related
* Delete code that was unused
Update integration tests for changes to ripple-lib account request API:

Account requests expect an object as first argument
Changed doc/rippled-example.cfg to specify default for ssl_verify
Add basic_client HTTP client