[Checkers] new name for the Custom checker

[Mahmood Ali]

> So far, other possibilities include Simple
> checker, User checker, and Basic checker.

I really like Basic Checker, and find it more preferable than the  
rest.  Adam in the presentation hinted at the name too.

Evaluation:
Simple Checker:  Simple is quite vague, in temrs of functionality,  
usage, design?
User Checker:    It does not describe the functionality of the checker
Basic Checker: 	 means checker with the most basic functionality a  
type checker should have
CommandLineChecker:	Describes usage rather than capabilities

- Mahmood