Added

• Classes PercentageVariable and PercentageReference
  • Uses floats in the range [0..1]
  • Custom editor property drawer that uses a slider
• Functions SetFixedValue and SetVariable on ValueReference
• Virtual property defaultValue on ScriptableVariable
• Function ResetToDefault on ScriptableVariable
• Array and list extension method IndexOf to get the index of an element/item using a custom predicate

Changed

• Renamed TimerBehaviour to TimedBehaviour
• Renamed constantValue to fixedValue in ValueReference
• Renamed useConstant to useVariable in ValueReference
  • Defaults to false instead of true to match the existing logic
• Renamed array and list extension method IsAny to Contains
• Renamed array and list extension method IsEach to ContainsAll
• Capitalized various property names
• Fixed documentation typos and grammar