A PlayerAttachment to deal with multiple capitals. The Value is the minumum number of capitols that must be held in order to be able to produce. Example: It is similar to retainCapitalNumber, but only affect gaining income and producing units (probably should be less than or equal to retainCapitalNumber) If a player has no playerAttachment, then it defaults to 1 (ie: you keep collecting and producing units so long as you control at least 1 capital)