Refactor LedgerEntrySet:

* Remove duplicate:
    This changes behavior to fix an apparent bug. The
    copy will now correctly inherit mParams instead
    of reverting to tapNONE

* Tidy up LedgerEntrySet declarations
* Tidy up TransactionEngine
* Tidy PathCursor declarations
* Add LedgerEntrySet::apply
* Add LedgerEntrySet ctor
* Add Keylet, keylet namespace
* Add defaulted copy members
* Use optional in TransactionEngine
* Use optional<LedgerEntrySet> in PathState
* Return shared_ptr in Ledger::fetch
* Don't call entryCache with zero
* Deprecate invalidate
* Remove default constructor
* Remove unused container API
* Remove CountedObject base class
* Remove insert, clear
* Remove entryCreate overload
* Remove unused and tidy up STLedgerEntry
* Make getEntry private and tidy
* Replace members with adjustOwnerCount free function
* Replace accountFunds with funds free function

src/ripple/app/tx/impl/OfferStream.cpp

@@ -122,8 +122,8 @@ OfferStream::step ()
         // Calculate owner funds
         // NIKB NOTE The calling code also checks the funds, how expensive is
         //           looking up the funds twice?
-        STAmount const owner_funds (view().accountFunds (
-            m_offer.owner(), amount.out, fhZERO_IF_FROZEN));
+        auto const owner_funds = funds(view(),
+            m_offer.owner(), amount.out, fhZERO_IF_FROZEN);
 
         // Check for unfunded offer
         if (owner_funds <= zero)
@@ -131,7 +131,7 @@ OfferStream::step ()
             // If the owner's balance in the pristine view is the same,
             // we haven't modified the balance and therefore the
             // offer is "found unfunded" versus "became unfunded"
-            auto const original_funds = view_cancel().accountFunds (
+            auto const original_funds = funds(view_cancel(),
                 m_offer.owner(), amount.out, fhZERO_IF_FROZEN);
 
             if (original_funds == owner_funds)