Support for "autosaving" Fieldmanager fields

When a project starts using Fieldmanager as a replacement to core admin interfaces, it makes sense to replicate core's autosave experience to prevent lost data.

Our particular use case is that we're using Fieldmanager repeatable groups to build listicles. A substantial amount of editorial effort goes into producing these, and it sucks when a browser crash loses the effort.

http://garlicjs.org/ library might be one approach to consider. Ideally though, the implementation would save to the database so the autosave persists between users.