Update dependent models/libraries in srcExternal #92
Description
srcExternal includes IRI and GEOPACK. Both appear to be pretty well out of date.
We should probably have a test that engages code calling these, and then we should update to recent versions.
IRI source: http://irimodel.org/IRI-2016/
GEOPACK source: http://geo.phys.spbu.ru/~tsyganenko/Geopack-2008_dp.for