Name munging is never undone

[mgree]

The JSON object { ".": 5 } will create a file named dot holding the number 5... but it will dump back to JSON without restoring the name.

The best solution is probably to track an "unmunged" name, and files that don't undergo a rename call go back exactly how they were.

This unmunged name is metadata, so the appropriate mechanism for working with it is up in the air (see #2).

[mgree]

fad45be introduces a (more or less hidden) way to ignore files when serializing the FS back (really, to be able to ignore ._* files on macOS). Related but not identical to name munging.