beast cleanup and tidying:

* Replace custom types with C++11 <cstdint> types
* Fix sqlite integer intos and uses
* Fix String implicit integer constructors
* Escape the enclosing namespace in sqdb
* Replace contract checks with assert
* Make many header files compile independently
* Remove the dependence on beast_core.h in many places
* Remove unused or obsolete classes and functions
* Remove unused or obsolete macros
* Remove unused network functions and files
* Remove unused or obsolete classes:
  - ChildProcess
  - HighResolutionTimer
  - InterProcessLock
  - Throw
  - TrackedMutex
  - UntrackedMutex
  - XmlDocument
  - XmlElement

src/ripple/validators/api/Manager.h

@@ -20,6 +20,9 @@
 #ifndef RIPPLE_VALIDATORS_MANAGER_H_INCLUDED
 #define RIPPLE_VALIDATORS_MANAGER_H_INCLUDED
 
+#include "../../beast/beast/threads/Stoppable.h"
+#include "../../beast/modules/beast_core/files/File.h"
+
 namespace ripple {
 namespace Validators {