[Refactor] Rename LoopAnnotator to ScopAnnotator

  The LoopAnnotator doesn't annotate only loops any more, thus it is
  called ScopAnnotator from now on.

  This also removes unnecessary polly:: namespace tags.



git-svn-id: https://llvm.org/svn/llvm-project/polly/trunk@218878 91177308-0d34-0410-b5e6-96231b3b80d8