Enable reconfiguration of rules mid-session

The rules of a dbfwfilter instance should be modifiable and those modification should take effect immediately on all sessions of that instance.

This could be achieved by using a globally shared map of file name to rule definition. This way the rules could be updated by modifying the rule file and reloading or creating a new filter which uses that file. This will incur a performance penalty but it should allow rules to be modified for open sessions.