Tidy up usage of std::begin, std::end
Levelization, improve structure of source files:

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
Prevent passing of non-POD types to POD-only interfaces:

This tidies up the code that produces random numbers to conform
to programming best practices and reduce dependencies.

* Use std::random_device instead of platform-specific code
* Remove RandomNumbers class and use free functions instead
Set version to 0.26.5-rc1
Remove unused sitefiles module
Remove beast::Atomic (RIPD-728)
[FOLD] Cleanup SharedObject documentation
[FOLD] Remove beast::Atomic from beast::ServiceQueueBase
[FOLD] Remove beast::Atomic from beast::ThreadLocalValue
[FOLD] Remove beast::Atomic from beast::CharPointer*
[FOLD] Use std::atomic_thread_fence instead of beast::memoryBarrier
[FOLD] Remove Atomic.h!
[FOLD] Remove ServiceQueue
[FOLD] Remove affinity support from beast::Thread
[FOLD] Remove priority support from beast::Thread
[FOLD] Make beast::Thread use std::string
[FOLD] Remove beast::String from beast::Thread
[FOLD] Remove beast::Thread::getCurrentThread
[FOLD] Remove beast::Thread::sleep and beast::Time::waitForMillisecondCounter
[FOLD] Simplify interface by removing unused params & functions