Allow spaces in the project path (fixes #6)

Author: sharwell

runtime/CSharp/Antlr4BuildTasks/Antlr4ClassGenerationTaskInternal.cs

@@ -243,11 +243,11 @@ public bool Execute()
 
                 List<string> arguments = new List<string>();
                 arguments.Add("-cp");
-                arguments.Add(ToolPath);
+                arguments.Add('"' + ToolPath + '"');
                 arguments.Add("org.antlr.v4.CSharpTool");
 
                 arguments.Add("-o");
-                arguments.Add(OutputPath);
+                arguments.Add('"' + OutputPath + '"');
 
                 if (GenerateListener)
                     arguments.Add("-listener");