RFE: mass prisoner escape as monthly special event

[SuperStucco]

A little something to add more flavor to a campaign - have a "Mass Prison Break!" as one of the potential monthly events. When this happens (only when prisoners are present), some or all of the prisoners who are not willing to defect are removed from the roster i.e. escaped. If someone wants to be clever a number of other options can be provided:

• determine the percentage of escapees using available guards (conventional infantry units)
• potential injuries/death for those who do not escape including those willing to defect
• different odds of event happening based on factors like enemy morale