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/interaction/keybindingmanager.h

@@ -69,11 +69,12 @@ public:
     static scripting::LuaLibrary luaLibrary();
 
     void keyboardCallback(Key key, KeyModifier modifier, KeyAction action);
+    
+    std::string generateJson() const override;
 
     const std::multimap<KeyWithModifier, KeyInformation>& keyBindings() const;
 
 private:
-    std::string generateJson() const override;
 
     std::multimap<KeyWithModifier, KeyInformation> _keyLua;
 };