Legacy workarounds for Visual Studio non thread-safe initialization
of function local objects with static storage duration are removed:
* Remove LeakChecked
* Remove StaticObject
* Remove SharedSingleton
Beast includes a lot of code for encapsulating cross-platform differences
which are not used or needed by rippled. Additionally, a lot of that code
implements functionality that is available from the standard library.
This moves away from custom implementations of features that the standard
library provides and reduces the number of platform-specific interfaces
andfeatures that Beast makes available.
Highlights include:
* Use std:: instead of beast implementations when possible
* Reduce the use of beast::String in public interfaces
* Remove Windows-specific COM and Registry code
* Reduce the public interface of beast::File
* Reduce the public interface of beast::SystemStats
* Remove unused sysctl/getsysinfo functions
* Remove beast::Logger
* Rename unity files
* Move some modules to new subdirectories
* Remove obsolete Visual Studio project files
* Remove obsolete coding style and TODO list
