Add folder rename endpoint

[reganwolfrom]

We are able to rename documents with PATCH /documents/{id} by specifying a new path, but there is currently no way to rename folder index items. Ideally, we would have an endpoint such as this: /indices/folder/rename that accepts the full path parameter and a folder name (no path) and renames the folder.

Conversely, we could allow a new full path that could function as a "mv" command, but this functionality is already available using POST /indices/folder/move

Since "path" is stored on the document level as well. Potentially would have to update all the documents "path" as well.