RE: the conversation around #61 , it seems like a good idea to attack the problem of the fact that the application negation prefix is hardcoded.

Furthermore, even when we make it configurable, there remains the issue of needing some way to escape these "special prefix" characters.

This is easy enough to implement but yaml is not big on "escaping" things so I'm not sure how to do this idiomatically. I think the solution that would appear obvious to most users is / but I'd appreciate feedback on that.

An alternative (although much much more involved approach) would be to alter the way the filesystem backend works such that ~applications subclass scalars and ~keys subclass keys.

on reflection it also seems clear that if we make all of these configurable, although it's not ideal, we could wontfix this issue an have there be no escape sequence on the grounds that there's plenty enough space on the keyboard to pick something that is still a valid hash key