Added tooltip to contract clauses indicating that they can't be manually adjusted

-Added rule to toggle whether refusing Martial Service also means that the vassal won't serve as Marshal
-Fixed another little thing re: vassals who are exempt from providing levies that was preventing the obligation restoration letter from going out to the liege

-Added rule to adjust the percentage of levies withheld when a vassal is Withholding Levies
-Tweaked the series of events for refusing martial service so that the vassal in question won't resign from council before the notice goes out to the liege

-Threshold rule now works
-Fixed issue where vassals who were exempt from levy obligations weren't being seen by the improvement check

-Created two game rules - the first for opinion debuff severity, the other for effect thresholds. Only the debuff severity rule does anything, currently.
-Fixed a syntax error in previous update

-Fixed an issue where refusal notifications were being spammed monthly from vassals exempt from providing levies

-Fixed the issue where multiple notices/decisions were being populated in situations where wars were declared simultaneously (specifically if one had started a new game and they or their liege immediately happened to be in multiple wars)
-Changed the wording of the letter from vassal -> liege when they restore their obligations after refusing levies/martial service because I was still unhappy with it.

-Added a cooldown to refusing levies so that if one had refused levies before they will consider it, again, after a year at war (also clears the associated flag from characters so that it doesn't potentially linger on them forever)
-Vassals exempt from providing levies will no longer trigger the Withholding Levies or Refusing Levies effects (still need to adjust some notifications to reflect this change)
-Added notifications to vassals when their levy obligations are reduced or restored
-Removed an unnecessary check for the on_game_start on_action
-Fixed an incorrect flag being set for monthly war checks on game start
-Converted some code that was used multiple times into macros

Made a minor adjustment to the language in the letter notifying the liege that a vassal who had refused levies is providing them again.

Vassals who had completely refused levies and martial service will now, if and when they restore their obligations, send a letter to their liege announcing it.