[Checkers] Checkers Framework improvements

[Michael Ernst]

When I was in Amsterdam on Wednesday, some people asked me to show them the
implementation of some of the checkers.  I had some trouble finding my way
around them, which was embarrassing.  I notice that they are looking better
today (when I looked over them to give some suggestions) than they did
then.  Thanks for the improvements!

I notice that there are still some problems, though.  There are still a
fair number of methods without Javadoc.  (As just one example, see methods
in AnnotatedTypeFactory, and that class lacks an overview indicating just
what it does or how one should go about customizing it.  The reference to
the manual isn't helpful for it, either.  But I don't want to pick on it;
other classes have similar problems.)  I would like to read and understand
the checkers framework and the checkers themselves, so I would really
appreciate it if everyone could make an effort to write the missing Javadoc
in the near future.

                     Thanks,

                    -Mike