Removed code for DataAnnotations, and will move to new assembly; turns out Windows Phone 8 doesn't have support for System.ComponentModel.DataAnnotations.
Changed EntityRuleSet.ValidateSpecifications back to EntityRuleSet.Validate in light of DataAnnotations not being supported on Windows Phone.
Completed String Required fluent code.
Completed Required, MinimumLength, MaximumLength, and MatchesPattern fluent specification validations.
Fixed a few invalid XML comments, and a misconfigured unit test.