Fix public member names of RPC::Context.

Conflicts:
	src/ripple/rpc/handlers/AccountTx.cpp
	src/ripple/rpc/handlers/AccountTxOld.cpp
	src/ripple/rpc/handlers/Ledger.cpp
	src/ripple/rpc/handlers/LedgerData.cpp
	src/ripple/rpc/handlers/RipplePathFind.cpp
	src/ripple/rpc/handlers/ServerInfo.cpp
	src/ripple/rpc/handlers/ServerState.cpp
	src/ripple/rpc/handlers/Submit.cpp
	src/ripple/rpc/handlers/Subscribe.cpp
	src/ripple/rpc/handlers/TxHistory.cpp
	src/ripple/rpc/handlers/Unsubscribe.cpp
	src/ripple/rpc/impl/Context.h
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.

Conflicts:
	src/ripple/rpc/handlers/RipplePathFind.cpp
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.
Remove unused isXRP(Issue) function.
Fix compilation errors in RPC/RipplePathFind.cpp
Adjust SSL context generation for Server:
The creation of self-signed certificates slows down the command
line client when launched repeatedly during unit test.
* Contexts are no longer generated for the command line client
* A port with no secure protocols generates an empty context
Add missing includes.
Refactor the structure of source files:
* New src/ripple/crypto and src/ripple/protocol directories
* Merged src/ripple/common into src/ripple/basics
* Move resource/api files up a level
* Add headers for "include what you use"
* Normalized include guards
* Renamed to JsonFields.h
* Remove obsolete files
* Remove net.h unity header
* Remove resource.h unity header
* Removed some deprecated unity includes