Add daemon mode option for optaplanner-wb's solver configuration

Currently there is no support for enabling daemon mode for optaplanner solver configuration xml file. When the solver configuration file is created using both "Add Asset" or "Import Asset", there is no such option to enable daemon mode. Imported solver configuration xml file will have the line "<daemon>true</daemon>" ignored.

Having daemon mode option in optaplanner-wb would be much appreciated for beginners like me to test out real-time planning features.