Feature/documentation topic (#822)

- Implement documentation topic that can be used to query documentation using the network API.
- Implement a way to pass arguments to lua scripts using json (rather than formatting entire lua string clientside)
- Implement ability to attach callback to lua script executions
- Implement abillity to transport return values from lua scripts back to network API clients.
- Do not initialize server interface on slave nodes.
- Implement Dictionary -> json converter using nlohmann json library

include/openspace/util/camera.h

@@ -33,7 +33,6 @@
 namespace openspace {
 
 class SceneGraphNode;
-class SyncBuffer;
 
 /**
  * This class still needs some more love. Suggested improvements:

include/openspace/util/factorymanager.h

@@ -110,9 +110,9 @@ public:
      */
     template <class T>
     ghoul::TemplateFactory<T>* factory() const;
-
-private:
+    
     std::string generateJson() const override;
+private:
 
     /// Singleton member for the Factory Manager
     static FactoryManager* _manager;