Added remotecontrol plugin to josm core. This plugin was initially written by Frederik Ramm (frederik) and incorporates code taken from YWMS plugin by frsantos. Major contributions by Bodo Meissner (bomm) and stephankn. Note: The code has been added, but is not "active" yet (RemoteControl.on == false). This is because wmsplugin and imagery plugin has not been adapted to this change. They are about to be integrated as well, so this adaption is not necessary.