Rename object

Can`t change name and extension of object file when editing object.
This causes to some troubles when we can change file in object storage to file of another type, and then we will download it.

Steps for example:
1. Create Container in Object Store.
2. Create object from raster image file: "Selection.png"
3. Edit object: change file to vector drawing "splines.dxf"
None that object name is grayed-out.
4. Update Object.
5. Click Download.
As result we have downloaded vector drawing with name and extension of raster PNG file.

It's happening when we call swift-function https://github.com/openstack/horizon/blob/master/openstack_dashboard/api/swift.py#L286 (in swift https://github.com/openstack/python-swiftclient/blob/master/swiftclient/client.py#L1402), because we send old name. If we will send new name -- swift will create a new object.
We need to be able change name.