Cleanups:

* Reduce Beast dependencies
* Remove unnecessary includes
* Don't use deprecated bassert macros
* Don't use beast::String in Json::Value

src/ripple/core/impl/Job.cpp

@@ -19,6 +19,7 @@
 
 #include <BeastConfig.h>
 #include <ripple/core/Job.h>
+#include <cassert>
 
 namespace ripple {
 
@@ -57,7 +58,7 @@ JobType Job::getType () const
 
 Job::CancelCallback Job::getCancelCallback () const
 {
-    bassert (m_cancelCallback);
+    assert (m_cancelCallback);
     return m_cancelCallback;
 }