Tidy up includes and add modules to the classic build:

An alternative to the unity build, the classic build compiles each
translation unit individually. This adds more modules to the classic build:

* Remove unity header app.h
* Add missing includes as needed
* Remove obsolete NodeStore backend code
* Add app/, core/, crypto/, json/, net/, overlay/, peerfinder/ to classic build

src/ripple/protocol/impl/TER.cpp

@@ -17,6 +17,7 @@
 */
 //==============================================================================
 
+#include <BeastConfig.h>
 #include <ripple/protocol/TER.h>
 
 namespace ripple {