Multiple history files and restart

[arango]

Added additional code to append new records to existing NetCDF files when writing multiple output (history, averages, and diagnostics) files. This only affects runs that were terminated suddenly and restarted with the last available record. The new code adds the records needed to finish such multiple output files. Many thanks to J.Paul Rinehimer for reporting this ​problem.

I also improved the error message when input fields are not found in multiple forcing NetCDF files. It was reporting the last file in the list. Now it reports all the files searched.