Unify the codepaths that format new/modified/changed sections and
conflicted paths in the "git status" output and make it possible to
properly internationalize their output.
* jn/wt-status:
wt-status: lift the artificual "at least 20 columns" floor
wt-status: i18n of section labels
wt-status: extract the code to compute width for labels
wt-status: make full label string to be subject to l10n