Fix some issues reported by lintian

Fix some issues reported by lintian

• Trim trailing whitespace. (trailing-whitespace)
• Bump debhelper from old 12 to 13. (package-uses-old-debhelper-compat-version)
• Set upstream metadata fields: Archive, Contact, Name. (upstream-metadata-file-is-missing)

Debdiff

These changes affect the binary packages:

[The following lists of changes regard files as different if they have different names, permissions or owners.]

Files in second set of .debs but not in first

-rw-r--r--  root/root   /usr/lib/debug/.build-id/b7/2f90f861cfdc9d2a4c5b8ea22ffb45e6ed132a.debug

Files in first set of .debs but not in second

-rw-r--r--  root/root   /usr/lib/debug/.build-id/37/2244a63d8d0b35b30f614b4eb537b5ccac280d.debug

No differences were encountered between the control files of package **r-cran-date**

Control files of package r-cran-date-dbgsym: lines which differ (wdiff format)

• Build-Ids: 372244a63d8d0b35b30f614b4eb537b5ccac280d b72f90f861cfdc9d2a4c5b8ea22ffb45e6ed132a

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Build and test logs for this branch can be found at https://janitor.debian.net/lintian-fixes/pkg/date/ad03c32c-6e7a-4187-af32-885de4502471.