Watch task completion notifications and safer theme migration

• It was difficult to integrate with other tools such as LiveReload when a batch of uploads have been performed by the watcher. You can tell theme watch to touch a file as a notification event. This is done by simply including the argument -notify=file-you-wish-to-touch-on-idle.
• Makes the operation of migrating a theme configuration from the old layout to the new environment based one safer. Before a migration is to be performed, the user will be prompted by to verify that the changes are sane. On confirmation, the changes will be written to disk.