Support TOP n When Initializing Edit Sessions (#290)

* Start of edit initialize filtering

* Implementation to utilize filtering

* Unit tests for the refactoring

* Unit tests for query construction

src/Microsoft.SqlTools.ServiceLayer/EditData/Contracts/EditInitializeRequest.cs

@@ -12,6 +12,11 @@ namespace Microsoft.SqlTools.ServiceLayer.EditData.Contracts
     /// </summary>
     public class EditInitializeParams : SessionOperationParams
     {
+        /// <summary>
+        /// Filtering parameters
+        /// </summary>
+        public EditInitializeFiltering Filters { get; set; }
+
         /// <summary>
         /// The object to use for generating an edit script
         /// </summary>