IDEA-100655 Mercurial plugin (hg4idea) shouldn't ask confirmation for removing non-version files.

*Change skipUnversionedAndNotUnderHg method argument to List<FilePath> unversionedFiles, because all VirtualFiles in filesToFilter are null. So we cannot use contains method of ChangeListManager.getUnversioned, it always return false. (see FilePathImpl constructor if forDeleted var set to true).