Resources were copied using make rules.  This is sensible in local
machine builds but non-optimal in cluster builds.  It is entirely IO
bound so that instead of benefitting from running on the cluster it
simply creates more IO as files need to be transferred over the network,
possibly multiple times.

This change introduces the <finalcopy> tag to the log which the frontend
reads in a new "default" filter called FilterCopyFile.  Thus the python
frontend does the copying rather than the cluster build engine.

This happens at the end of each invocation of the build engine or "stage".
Since resources are built in their own stage, the copying is completed
before build tasks in the other stages require them.  The copied files
are not needed in the resource stage itself.

The filter uses <progress:end ...> tags to determine when a stage
is finished and this requires that the timing feature be switched on
permanently.

The format of the tag is:
<finalcopy source="sourcefilename">dest_filename1 dest_filename2 ...</finalcopy>

Spaces may not be used in filenames. The sequence "%20" may be used
instead.
