Double meaning for slashes with new regex syntax

[ppcad]

The new regex syntax requires filters to have the form "/REGEX/".
To do this it checks if a term begins and ends with a /.
This leads to problems if the filter term has slashes, but shouldn't be treated as regex (i.e. "/some/path/").

Here are some ideas how this could be implemented:

1. Add escaping for slashes in the rules ("\/some/path\/") and remove them after the regex check
2. Don't use " for regex, but only /: So /REGEX/ instead of "/REGEX/"

I prefer idea 2.
Right now omitting the quotation marks leads to a crash of Logprep without an explanation that it was caused by a filter syntax error.