refactor(EnvelopeHistory): rename as History

EnvelopeGenerator.Domain/Entities/Document.cs

@@ -19,7 +19,7 @@ public class Document
     public Document()
     {
 #if NETFRAMEWORK
-        Elements = Enumerable.Empty<DocumentReceiverElement>().ToList();
+        Elements = Enumerable.Empty<Signature>().ToList();
 #endif
     }
 
@@ -35,7 +35,7 @@ public class Document
     [Column("BYTE_DATA", TypeName = "varbinary(max)")]
     public byte[] ByteData { get; set; }
 
-    public List<DocumentReceiverElement> Elements { get; set; }
+    public List<Signature> Elements { get; set; }
 
     // TODO: * Check the Form App and remove the default value
     [NotMapped]