MIRTH-3326: Added the ability to host static resources on the HTTP Listener. Users can specify a context path, resource type, value, and content type, and any requests coming in that match the context path will automatically return the configured value. There are three resource types: File, Directory, and Custom. File just returns a specific file, while Directory allows clients to request any file in a directory (subdirectories are not included). Custom allows any arbitrary string to be returned. All fields are replaceable with Velocity.