[Checkers] @ImplicitFor meta-annotation

[Mahmood Ali]

sounds great, and i do give full support.  i also like having one  
annotation with multiple arguments.

there are two issues now
1. how does implicitfor overlap with default.  in igj for example,  
placeholder is implicit in constructors only when no qualifier is  
found.  can we have implicitfor[all] default for everything if there  
is no other default

2. now that we have annotationsrelations, we should propagate it to  
the factory which can utilize to to check within an annotation exists  
or not. similarly for implicitfromclass.

regards,
mahmood