Add delimiters for wildcard search

Auto-adding % wildcard at the beginning and the end of a search string by default via "before=>true, after=>true" is sure nice.
But the it also needs a way to disable it from the search field. Delimiter $ (configurable) in this case.

I could also have used a char like pipe (`|`). But this feature is probably mainly for admin filters and the $ is borrowed from the regex ending char.

See the documentation below for details.