Skip TBB files from remote stations on read-in

[MijnheerD]

Issue being addressed

When globbing over all TBB files in the directory, it is possible for a bunch of remote station files to be included in the all_tbb_files list. When doing the pattern matching

re.findall(r"CS\d\d\d", tbb_filename)

on those files, the result is an empty list. When then calling the first element, the reader crashes.

Proposed solution

I changed the code to either take the first element of the resulting list, or default to None in case the list is empty. If the station_name is None, the file is assumed to be from a remote station and skipped. Is this desired behavior? Should we explicitly check that the pattern "RS\d\d\d" does appear in the file name and do something else with it?

[MijnheerD]

The changes from this PR have been included in #679