Add IHasChangedWhen support and cleanup using statements

Introduced IHasChangedWhen interface to EnvelopeReceiver and History.
Added HasEmailAndName property to EnvelopeReceiver.
Updated AutoMapperAuditingExtensions to map ChangedWhen to UTC.
Removed redundant using statements and fixed formatting.

EnvelopeGenerator.Domain/Entities/EnvelopeReceiver.cs

@@ -3,6 +3,7 @@ using System.ComponentModel.DataAnnotations;
 using System.ComponentModel.DataAnnotations.Schema;
 using DigitalData.Core.Abstractions.Interfaces;
 using EnvelopeGenerator.Domain.Interfaces;
+using EnvelopeGenerator.Domain.Interfaces.Auditing;
 
 namespace EnvelopeGenerator.Domain.Entities
 {
@@ -86,6 +87,8 @@ namespace EnvelopeGenerator.Domain.Entities
 
         [NotMapped]
         public bool HasEmailAndName =>
+            !string.IsNullOrWhiteSpace(Receiver.EmailAddress) &&
+            !string.IsNullOrWhiteSpace(Name);
         #endregion
     }
 }