Autobridging uses XRP as a natural bridge currency to allow IOU-to-IOU orders
to be satisfied not only from the direct IOU-to-IOU books but also over the
combined IOU-to-XRP and XRP-to-IOU books.
This commit addresses the following issues:
* RIPD-486: Refactoring the taker into a unit-testable architecture
* RIPD-659: Asset-aware offer crossing
* RIPD-491: Unit tests for IOU to XRP, XRP to IOU and IOU to IOU
* RIPD-441: Handle case when autobridging over same owner offers
* RIPD-665: Handle case when autobridging over own offers
* RIPD-273: Groom order books while crossing
Source files are moved between modules, includes changed and added,
and some code rewritten, with the goal of reducing cross-module dependencies
and eliminating cycles in the dependency graph of classes.
* Remove RippleAddress dependency in CKey_test
* ByteOrder.h, Blob.h, and strHex.h are moved to basics/. This makes
the basics/ module fully independent of other ripple sources.
* types/ is merged into protocol/. The protocol module now contains
all primitive types specific to the Ripple protocol.
* Move ErrorCodes to protocol/
* Move base_uint to basics/
* Move Base58 to crypto/
* Remove dependence on Serializer in GenerateDeterministicKey
* Eliminate unity header json.h
* Remove obsolete unity headers
* Remove unnecessary includes
