Should be able to call Singularize and Pluralize on singular and plural words respectively

[MehdiK]

Currently calling Singularize on a singular word returns null or an incorrect value (e.g. "Process".Singularize() => "Proces". Same goes for Pluralize on a plural word (e.g. "men".Pluralize() => "mens")

Ideally we need to implement IsPlural and/or IsSingular extension methods. This way we can fix this issue using the methods and the users of the framework can use the new methods to check a word without having to call Singularize or Pluralize on it.