Adding schema validation to the DatabaseSchemaCreation class.

Helps determine if valid database exists and which version it corresponds to.
On startup the legacy connectionstring is used if one exists, so its not ignore but rather reconfigured.
Relates to U4-1520.

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

@@ -151,6 +151,26 @@ namespace Umbraco.Core.Persistence.SqlSyntax
             return "NVARCHAR";
         }
 
+        public virtual IEnumerable<string> GetTablesInSchema(Database db)
+        {
+            return new List<string>();
+        }
+
+        public virtual IEnumerable<ColumnInfo> GetColumnsInSchema(Database db)
+        {
+            return new List<ColumnInfo>();
+        }
+
+        public virtual IEnumerable<Tuple<string, string>> GetConstraintsPerTable(Database db)
+        {
+            return new List<Tuple<string, string>>();
+        }
+
+        public virtual IEnumerable<Tuple<string, string, string>> GetConstraintsPerColumn(Database db)
+        {
+            return new List<Tuple<string, string, string>>();
+        }
+
         public virtual bool DoesTableExist(Database db, string tableName)
         {
             return false;