journal files can now include journal, timeclock or timedot files (but
not yet CSV files). Also timeclock/timedot files no longer support
default year directives.
The Hledger.Read.* modules have been reorganised for better reuse.
Hledger.Read.Utils has been renamed Hledger.Read.Common and holds
low-level parsers & utilities; high-level read utilities have moved to
Hledger.Read.
Currently this is just the journal and timelog file formats. This is more
scalable, but when things go wrong there is no longer just a single parse
error. For now we'll just show the first error, the one from the journal
file parser.