WL-3230 Stop trying to delete the old file

When receiving a PUT request then we shouldn't need to delete the old file,
let's just send the input stream to the existing file.
WL-3230 Edit the existing resource

Instead of adding a new one.
WL-3230 Don't set up old properties

No need to set up properties again because we don't lose them now.
WL-3230 Determine whether this is a new file

Currently the `ContentHostingService.editResource` throws a permission
exception when it should throw an id unused exception.

So we test it first with getResource to see if the file exists.

This can be fixed when KNL-1217 is fixed.
WL-3230 Set the copyright and display name

Organise this logic so that it all appears in the same place.
Merge pull request #1 from ox-it/WL-3230

WL-3230 Persist existing file settings