Add a `resourcesToExpunge` item to the `Result` attribute of operations,
and have the `Operation` base class remove resources from the
resource manager after operation observers have run, and before releasing
resource locks, to avoid conflicts. Rework the `RemoveResource`
operation to use this mechanism, and have `File .. Close Resource` use
this operation instead of closing resources directly.

Because `Operation` now accesses the resource manager, there is no need
for the `ResourceManagerOperation` sub-class, so alias it to `XMLOperation`.