lib-master: Add improved log filter parsing

lib-master: Add improved log filter parsing

It now supports parenthesis to perform ANDs within a query. For example:
"(ruleA1 ruleA2) ruleB (ruleC1 ruleC2 ruleC3)" has 3 ORed rules.

Rules can contain:

 - event:<name>
 - source:<filename>[:<line number>]
 - field:<key>=<value> can be used multiple times
 - cat[egory]:<value> can be used multiple times

For example:

event:http_request_finished (cat:error cat:storage)

This matches either the "http_request_finished" named event, or
alternatively any error event that belongs to "storage" category.