Converter::Rename only renames the first element

[scpeters-test]

Original report (archived issue) by Steve Peters (Bitbucket: Steven Peters).

---

During review of pull request #551, which fixed the Converter::Remove function to remove repeated elements, @azeey pointed out that Converter::Rename has the same problem in that it only renames the first element and not any repeated elements. I have confirmed this by adding a failing test to the following branch:

• https://scpeters-test.github.io/gh-pages_sdformat_fast_export/#!/osrf/sdformat/branch/converter_fix_rename?dest=converter_fix_remove#diff