U4-4847 Refactor ContentService (#1266)

* U4-4748 - refactor Content-, Media- and MemberTypeRepository

* Cleanup Attempt

* Cleanup OperationStatus

* U4-4748 - refactor Content-, Media- and MemberTypeService

* U4-4748 - cleanup locking

* U4-4748 - refactor Content-, Media- and MemberRepository

* U4-4748 - refactor ContentService (in progress)

* U4-4748 - all unit of work must be completed

* U4-4748 - refactor locks, fix tests

* U4-4748 - deal with fixmes

* U4-4748 - lock table migration

* Update UmbracoVersion

* Fix AuthorizeUpgrade

* U4-4748 - cleanup+bugfix lock objects

* U4-4748 - bugfix

* updates a string interpolation

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

@@ -11,14 +11,9 @@ namespace Umbraco.Core.Persistence.SqlSyntax
     /// <summary>
     /// Represents an SqlSyntaxProvider for Sql Ce
     /// </summary>
-    [SqlSyntaxProviderAttribute(Constants.DbProviderNames.SqlCe)]
+    [SqlSyntaxProvider(Constants.DbProviderNames.SqlCe)]
     public class SqlCeSyntaxProvider : MicrosoftSqlSyntaxProviderBase<SqlCeSyntaxProvider>
     {
-        public SqlCeSyntaxProvider()
-        {
-            
-        }
-
         public override bool SupportsClustered()
         {
             return false;
@@ -64,7 +59,10 @@ namespace Umbraco.Core.Persistence.SqlSyntax
             }   
         }
 
-        
+        public override string GetConcat(params string[] args)
+        {
+            return "(" + string.Join("+", args) + ")";
+        }
 
         public override string FormatColumnRename(string tableName, string oldName, string newName)
         {