Smarter and safer worldBackupRestore
Smarter and safer worldBackupRestore

  * Backup prior to restore is done outside worldBackupRestore
    to improve reusability of the method.
  * Restoration is cancelled if the world cannot be backed-up first
  * Restoration is done in a tmp dir first and world is overwritten
    only if successful
  * Fixes issue #82

MinecraftServerControl/mscs,bot190/mscs,seldonPlan/mscs,sandain/MinecraftServerControlScript