Changing the registry part of BSRegister to be a new inner class called BSVariableRegistry
* Register.php:
(BSRegister::__construct): Instantiate a new instance of BSVariableRegistry
(BSRegister::Registry): New method
(BSRegister::Register): Removed
(BSRegister::Unregister): Removed
(BSRegister::Get): Removed
(BSRegister::GetType): Removed
(BSRegister::GetAll): Removed
(BSVariableRegistry): New class
* docs/UnitTest/RegisterTest.php: Updated the unit test for the new BSRegister functionality