Add a wildcard `*`

[vendethiel]

If you want to limit some subkeys, but keep everything else, you currently have to do something like:

mask('a(b,c),-some_fake_key', %);

It'd probably be better to add this instead:

mask('a(b,c),*', %);

mask('*,a(b,c)', %);

[vendethiel]

Maybe that wildcard could also allow for partial searches, but that sounds less useful.
This would also allow mixing pos/neg.
Example:

mask('user_*,-password', %);