In TypoCorrectionConsumer, BestResults to CorrectionResults to lessen

the confusion among all of the uses of Best* in relation to the set of
possible typo correction results. Also add a method to return the set of
typo corrections that have the single best edit distance--it returns the
second half of the first pair in TypoEditDistanceMap (with
getBestEditDistance already returning the first half).

llvm-svn: 157781