Least harmful method of fixing '@' query notation.

The new '+@' query path prefix has a semantic behavior that is completely
different from the '@' query path prefix. This commit renames the '@' path
prefix to the '@@' prefix and adds the '@' path prefix
to perform the same function as the '+@' prefix only without collecting the results.
Merge pull request #82 from addthis/query-fix-notation

Least harmful method of fixing '@' query notation.