#47 Custom properties parsing failures management

[Whitehouse112]

Custom property parsing failures rework and refactoring. Added to the IParseFailureObserver the methods to notify the user if:

• a property value cannot be handled (e.g. int property receiving a string, a string property receiving an int, etc...)
• a provided enum value is not part of the enum values listed as valid
• a provided enum index is out of index (e.g. enum definition has 4 values, you provide index 5 as value)
• a provided property value is out of bound (e.g. int value is greater/lower than min/max value)

[Brainy0207]

Looks great. Thanks for the quick work.