Refactor song time texts

There are three:
1. About dialog
2. The main status bar
3. Library (in the item listings for genre, artist, and album views)

This updates the localization strings and should be more useful way to
handle for localizers.
Better translation support and formatting for time-related strings

Merge remote-tracking branch 'others/hobophobe/refactor_time_text'
i18n: the content of POTFILES.in is now stable (always sorted)
i18n: up-to-date French translation