This has been mostly done with changes in the datetime crate's suddenly
supporting locales.
It's still important that the user's locale is touched only once and
cached from that point on, so a struct in output::details has been made
public, along with that module. This will change later as that object
gains more and more uses thoughout the codes.
Use the `locale` crate as a dependency to read in the set
thousands-separator character, and pass this to the file size column,
which uses it to add the separators in.
en_GB uses ","
fr_FR uses "" and just displays the numbers in one go.
Using the datetime crate, add an extra column to the --long view that
prints out the modified, accessed, or created timestamp for each file.
Also, let the user pick which one they want to see based on the --time
command-line option.
