Allow IDENTITY_INSERT for SQL Server when making liquibase insert statements

Since there are IDENTITY columns in many tables, SQL Server prevents manual entry of ids into such columns. SQL Server provides SET IDENTITY_INSERT <tableName> ON for allowing inserting ids. Thus all insert statements done through liquibase needs to be checked and wrapped between:

SET IDENTITY_INSERT <tableName> ON;
insert...;
SET IDENTITY_INSERT <tableName> OFF;

Care should be taken to first check if there is an identity column in the table or else the SET IDENTITY_INSERT fails with exception.
This can be implemented through extensions in liquibase 2.0