Split off CheckLibraryVersions.test.cpp.
Remove unused sitefiles module
Reduce Beast dependencies by leveraging C++11 features:

* Remove beast::Atomic (RIPD-728):
  * Use std-provided alternatives
  * Eliminate atomic variables where possible

* Cleanup beast::Thread interface:
  * Use std::string instead of beast::String
  * Remove unused functions and parameters

* Remove unused code:
  * beast::ThreadLocalValue
  * beast::ServiceQueue
Remove legacy LoadTypes (RIPD-365)
Fix undefined behavior
Support a "no_server" flag in test config.
* Will use a running instance of rippled (possibly in a debugger).
* Modify all tests to respect the server_default value.
* Fail test if new account already exists and has a balance.
* README.md with instructions for advanced test debugging, particularly using no_server.
Avoid processing transactions if we need a network ledger

Not processing tranasctions without a network ledger makes
initial network synchronization faster.
Pathfinding bugfixes (RIPD-735):
* Fix specifying paths and search level for ripple_path_find
* Don't modify the pathfinder, it has issuer-neutral paths.
* Handle previous paths correctly
* Compare paths correctly