Fixes RePublishAll method to ensure it performs the same function as the legacy Document.RePublishAll - it just

re-generates the XML in the cmsContentXml table. Updates the Sql providers to support truncate table. Updates the RepublishAll
unit test. Adds a TruncateTable extension to PetaPoco. Adds locking to certain service methods that perform more than once function.

src/Umbraco.Core/Persistence/SqlSyntax/ISqlSyntaxProvider.cs

@@ -31,6 +31,7 @@ namespace Umbraco.Core.Persistence.SqlSyntax
         string InsertData { get; }
         string UpdateData { get; }
         string DeleteData { get; }
+        string TruncateTable { get; }
         string CreateConstraint { get; }
         string DeleteConstraint { get; }
         string CreateForeignKeyConstraint { get; }