Added the Decimal::mod() method, broadened Decimal::of()

Decimal::of() now accepts Decimal, float, and objects convertible to string.
Added a convenience method ValidationResult::isSuccess()
Completed the implementation of NumberValidator

- The validator now accepts decimal numbers
- The step is implemented
- This is backed up with unit tests
Added ability to remove min, max and step from the NumberValidator
Added default step of 1 and support for "any" to Input\Number