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

src/ripple/rpc/impl/TransactionSign.cpp

@@ -17,6 +17,7 @@
 */
 //==============================================================================
 
+#include <ripple/app/paths/FindPaths.h>
 #include <ripple/basics/StringUtilities.h>
 #include <ripple/rpc/impl/TransactionSign.h>
 #include <beast/unit_test.h>
@@ -151,22 +152,20 @@ static Json::Value signPayment(
             if (!lpf.isOk ())
                 return rpcError (rpcTOO_BUSY);
 
-            bool bValid;
             auto cache = std::make_shared<RippleLineCache> (lSnapshot);
-            Pathfinder pf (
+            STPath fullLiquidityPath;
+            auto valid = findPathsForOneIssuer (
                 cache,
-                raSrcAddressID,
-                dstAccountID,
-                saSendMax.getCurrency (),
-                saSendMax.getIssuer (),
-                amount, bValid);
+                raSrcAddressID.getAccountID(),
+                dstAccountID.getAccountID(),
+                saSendMax.issue (),
+                amount,
+                getConfig ().PATH_SEARCH_OLD,
+                4,  // iMaxPaths
+                spsPaths,
+                fullLiquidityPath);
 
-            STPath extraPath;
-            if (!bValid ||
-                !pf.findPaths (getConfig ().PATH_SEARCH_OLD,
-                               4,
-                               spsPaths,
-                               extraPath))
+            if (!valid)
             {
                 WriteLog (lsDEBUG, RPCHandler)
                         << "transactionSign: build_path: No paths found.";