* Support PreviousTxnID until the switchover
* Implement "No Ripple" for issue_iou and redeem_iou.
* Do not utilize issue_iou and redeem_iou from legacy code
* Rename 0.27.x legacy files to account for VS build process
* Misc. cleanups
Changes made to support autobridging and improve the offer-crossing and
pathfinding logic result in transaction-breaking changes which cause
incompatibilities between 0.27 and 0.28 builds of RippleD.
This patch simplifies deployment of 0.28 on the Ripple network by allowing
RippleD to emulate the 0.27 semantics while the last closed ledger closed
before March 30, 2015 at 13:00:00 PDT, after which time the new 0.28
semantics will become active.
The transaction-breaking changes addressed in this commit are:
3ccbd7c9b2b203db27a4
