fix a couple of odd behaviors of data frame transforms REST API's:
- check if id from body and id from URL match if both are specified
- do not allow a body for delete
- allow get and stats without specifying an id
The data frame plugin allows users to create feature indexes by pivoting a source index. In a
nutshell this can be understood as reindex supporting aggregations or similar to the so called entity
centric indexing.
Full history is provided in: feature/data-frame-transforms