Add from_ssc command for CEL scripts

scripts/tests/from_ssc.cel

@@ -0,0 +1,3 @@
+{
+   from_ssc { fragment "Modify \"433 Eros:Eros:1898 DQ\" \"Sol\" {UniformRotation {Period 0.01}}" }
+}

src/celengine/cmdparser.cpp

@@ -895,6 +895,12 @@ Command* CommandParser::parseCommand()
         paramList->getString("path", path);
         cmd = new CommandSetRingsTexture(object, texture, path);
     }
+    else if (commandName == "from_ssc")
+    {
+        string fragment;
+        paramList->getString("fragment", fragment);
+        cmd = new CommandFromSSC(fragment);
+    }
     else
     {
         error("Unknown command name '" + commandName + "'");

src/celengine/command.cpp

@@ -1175,3 +1175,20 @@ void CommandSetRingsTexture::process(ExecutionEnvironment& env)
         sel.body()->getRings()->texture = MultiResTexture(textureName, path);
     }
 }
+
+
+///////////////
+// FromSSC command
+CommandFromSSC::CommandFromSSC(string _fragment) :
+    fragment(_fragment)
+{
+}
+
+void CommandFromSSC::process(ExecutionEnvironment& env)
+{
+    Universe* u = env.getSimulation()->getUniverse();
+    if (u == nullptr)
+        return;
+    istringstream in(fragment);
+    LoadSolarSystemObjects(in, *u, "");
+}

src/celengine/command.h

@@ -813,4 +813,15 @@ class CommandSetRingsTexture : public InstantaneousCommand
     std::string object, textureName, path;
 };
 
+
+class CommandFromSSC : public InstantaneousCommand
+{
+ public:
+    CommandFromSSC(std::string);
+    void process(ExecutionEnvironment&);
+
+ private:
+    std::string fragment;
+};
+
 #endif // _COMMAND_H_