- Add copyright headers to files that did not already have them
- Update the year to the last year the file was modified in files with
existing headers.
As part of resolving a resource, record its MD5 hash in the output
metadata. In order to enable this, resource resolution is now done via
the context, rather than directly via the ResourceResolver (in order not
to introduce a context dependency in the Gui object, context now
emulates the resolver interface).