Correct archive dir path in preferences.
Start adding station time zone support.

Support specification of station time zones, including whether or not
DST is observed. Update ambiguous time detection to use this
information.

Move functions for checking date and time components to new `time_utils`
module.

Allow specification of names of stations to be excluded from archive.
Merge branch 'master' of https://github.com/HaroldMills/NFC.git