'Automatic alias' option for nodes is counter intuitive

Issue Summary

When disabling 'Automatic alias' for a node, the setting should be remembered for the next time the node is edited, it's unrealistic to expect the user to change the option every time. One side effect of this is that you have no way of knowing if the existing path is the automatic version or a custom one.

To reproduce:
1. In Pathauto general settings, set the update action to "Create a new alias. Delete the old alias."
2. Create a new page and add a title
3. In the URL path settings, turn off 'Automatic alias' and add a custom path
4. Save the node
5. Edit the node and notice that 'Automatic alias' has been enabled.