Refactor View, MetaView, and tx processing:

This tidies up the View interface and makes transaction
application a free function, with the removal of the
TransactionEngine class. A new class ApplyContext provides
all the state information needed to apply a Transactor. The
Transactor is refactored to perform all the processing
activities previously part of TransactionEngine.

The calculation of metadata from a MetaView is improved.
A new apply function performs all the steps for calculating
and inserting metadata into the tx map.

Transaction processing code path is passed a Config instead
of retrieving the global, and uses the Journal supplied in
the call to apply() consistently.

To support transaction processing and RPC operations, a
new POD type ViewInfo is added which consolidates static
information about open and closed ledgers, such as the ledger
sequence number or the closing times. Ledger and MetaView are
refactored to use this info.

The ViewInfo now contains the "open ledger" setting. The
tapOPEN_LEDGER ViewFlag is removed. The view property of
being an open ledger is obtained from the base or by using
the MetaView constructor which presents a closed ledger as
an open one.

View, MetaView:

* Fix missing includes
* Add apply free function
* Use Journal in TransactionEngine
* Use BasicView in TransactionEngine
* inline NetworkOPs::batchApply
* Add shallow_copy, open_ledger MetaView ctor tags
* Add ViewInfo with open flag, seq, close times
* Make parent_ a reference
* Tidy up ctor arguments and base_ name
* Remove tapOPEN_LEDGER
* add assert to MetaView::apply
* ViewInfo comment
* Throw, pass Journal in txInsert
* Add BasicView::txCount

TransactionEngine:

* Add apply
* Make TransactionEngine private
* Refactor MetaView::apply and apply()
* Rename to TxMeta
* Refactor treatment of metadata in MetaView, TransactionEngine
* Rename to ApplyContext
* Use ApplyContext& in Transactor
* Pass Config in ApplyContext
* Declare Transactor classes in headers
* Use view flags in Transactor

src/ripple/protocol/TER.h

@@ -25,10 +25,11 @@
 namespace ripple {
 
 // See https://ripple.com/wiki/Transaction_errors
-
-// VFALCO TODO consider renaming TER to TxErr or TxResult for clarity.
 //
-enum TER    // aka TransactionEngineResult
+// "Transaction Engine Result"
+// or Transaction ERror.
+//
+enum TER
 {
     // Note: Range is stable.  Exact numbers are currently unstable.  Use tokens.