Allow filter feeds for updating fields whose time change cannot be checked through the JQL

[chandler05]

The Problem

If a filter feed were to be created for updating Mojang Priority, we wouldn't be able to check it properly because no check exists for the time that the field was updated

Possible Solution

I propose having an optional second jql that the config defines, in this case it would be the following:

previousJql: "Mojang Priority" is EMPTY AND resolution = unresolved
jql: "Mojang Priority" is not EMPTY AND resolution = unresolved

The previousJql would be searched every run, but it would only affect the next run

The bot would search for tickets using the jql, and then if that same ticket appeared from the previous run's previousJql search, then it would be posted because that means it was updated after the last run