[DONE][Suggestion] Overrides for difficulty coefficient effects

[Meridian]

For a longer time, people have been asking for more control over difficulty coefficient impact on the Dogfight, especially UFO firing rates and UFO escape countdown.

These two have now been reworked and can operate also on a percentage base, instead of flat base.

Besides them, I have also added 4 more attributes related to difficulty coefficients.
Vanilla values are in the example below and can be modified easily.

You can use all, some or none of these new attributes.
If you don't use a particular attribute, the game will behave as until now for that particular functionality (100% back-compatibility).

Code: [Select]

difficultyCoefficientOverrides:
  ufoFiringRateCoefficients: [100, 95, 90, 85, 80]          # percent of default... percentages instead of vanilla flat values
  ufoEscapeCountdownCoefficients: [100, 95, 90, 85, 80]     # percent of default... percentages instead of vanilla flat values

  retaliationTriggerOdds: [4, 8, 12, 16, 20]                # vanilla percentages
  retaliationBaseRegionOdds: [50, 56, 62, 68, 74]           # vanilla percentages

  aliensFacingCraftOdds: [0, 20, 40, 60, 80]                # vanilla percentages

  monthlyRatingThresholds: [-900, -800, -700, -600, -500]   # vanilla points; please note that only NEGATIVE numbers are accepted here

https://www.ufopaedia.org/index.php/Ruleset_Reference_Nightly_(OpenXcom)#Difficulty_Settings