Add jasperlib as a required dependency for GRIB
Check that members.nl namelists have correct tags

The first column in members.nl should be consecutive numbers starting
from 0. This commit verifies that the namelists is correct.
Warn users when caching options are specified for InputFlat

InputFlat automatically caches other members and other offsets. Users
can therefore not specify these. Warn the user if other options are
attempted.