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

modules/server/servermodule.cpp

@@ -28,6 +28,8 @@
 #include <modules/server/include/connection.h>
 #include <modules/server/include/topics/topic.h>
 #include <openspace/engine/globalscallbacks.h>
+#include <openspace/engine/globals.h>
+#include <openspace/engine/windowdelegate.h>
 #include <ghoul/fmt.h>
 #include <ghoul/io/socket/socket.h>
 #include <ghoul/io/socket/tcpsocketserver.h>
@@ -86,7 +88,10 @@ void ServerModule::internalInitialize(const ghoul::Dictionary& configuration) {
             std::unique_ptr<ServerInterface> serverInterface =
                 ServerInterface::createFromDictionary(interfaceDictionary);
 
-            serverInterface->initialize();
+
+            if (global::windowDelegate.isMaster()) {
+                serverInterface->initialize();
+            }
 
             _interfaceOwner.addPropertySubOwner(serverInterface.get());
             
@@ -101,6 +106,10 @@ void ServerModule::internalInitialize(const ghoul::Dictionary& configuration) {
 }
 
 void ServerModule::preSync() {
+    if (!global::windowDelegate.isMaster()) {
+        return;
+    }
+
     // Set up new connections.
     for (std::unique_ptr<ServerInterface>& serverInterface : _interfaces) {
         if (!serverInterface->isEnabled()) {
@@ -165,7 +174,9 @@ void ServerModule::cleanUpFinishedThreads() {
 
 void ServerModule::disconnectAll() {
     for (std::unique_ptr<ServerInterface>& serverInterface : _interfaces) {
-        serverInterface->deinitialize();
+        if (global::windowDelegate.isMaster()) {
+            serverInterface->deinitialize();
+        }
     }
 
     for (ConnectionData& connectionData : _connections) {