[dev] Mnemo Category Patch

[Chuck Hagenbuch]

Quoting Andrew Coleman <mercury at appisolutions.net>:

> Mnemo is not saving the category when adding a new note. Same story as nag.
>
> Simple patch, too :)

Not quite the right one; there simply weren't enough format strings. I solved
the problem slightly differently by removing the _private fields, that we've
never used anyway.

-chuck

--
"Regard my poor demoralized mule!" - Juan Valdez