Small refactoring of the FluentExtensions namespace and tests.
Grouped the different predicates in namespaces. Renamed some of the files for better consistency.
Small change in the way we test what is the message of ValidationPredicateResult. Changed the messages for Positive/Negative infinity.
Refactored the messages. Now the values are surrounded by <>.
Refactored the imlementation for Positive/Negative infinity methods. Now we have less validation predicates.