Add logical object renaming feature

[karlcz]

a new POST /path/to/new/object handler takes a JSON command description:

  {
    "command": "rename_from",
    "source_name": "/path/to/orig/object",
    "versions": [ "version1", "version2", ..],
    "copy_acls": true
  }

and mirrors version records under the new object name, implemented as a logical rename (no bulk data copy/movement). The versions field is optional and it processes all versions by default. The copy_acls field is optional and defaults to false, where only basic ownership is set as in normal version uploads.

The implementation uses version.aux fields:

• rename_to: [ newname, newversion ]
• hname: original hatrac object name under which data is stored
• hversion: original hatrac object version under which data is stored

The old record links to the new one and only the new one is processed to serve content. During retrieval, the new record passes the original hatrac name information and aux metadata into the backend storage module.