Quiet checkpoint reading
If reading succeeds, it should write anything of interest to the log
file. If it does not, it should make a fatal error. Code here might
be run as part of mdrun (possibly in a multi-simulation), or grompp,
or compare, or dump, or eventually from an API caller, so we can't
make assumptions about what should be reported to a terminal.
Removed support for issuing a warning about restarting from very old
checkpoint formats, instead issuing a fatal error. Elsewhere, we
anyway observe that checkpoint restarts across major version
differences are not supported.
Change-Id: Id2b084bf0792a6992931609fb78d4a38a5f255fe