[Checkers] Checkers Names

[Mahmood Ali]

Hi Mike,

Should we change the name of the checkers for this release:  
InternedChecker --> InterningChecker, NonNullChecker -->  
NullnessChecker ?

Should we change the package names too: checkers.nonnull ->  
checkers.nullness?

I noticed interned having the qualified name  
'checkers.nonnull.quals.Interned'.  I assume that was a typo.  Should  
it have been in 'checkers.interned.quals.Interned' or interning?

I am a bit concerned about making such changes that affect the user  
significantly without having them in a development release first.

- Mahmood