CleanJosm()
Virtual task that coordinates deletion of the temporary JOSM preferences.
This task creates three subtasks with the same name as itself, only with the suffixes Cache, Pref and Userdata.
Each one of these subtasks deletes one of the directories defined at JosmPluginExtension.tmpJosmCacheDir,
JosmPluginExtension.tmpJosmPrefDir and JosmPluginExtension.tmpJosmUserdataDir.
This task depends on all three of these, so all subtasks run when you execute this task. But you can also run the subtasks individually by calling them directly.