Combine Time & Locale prefs

[humdinger]

As discussed at ​Gerrit.

The problem, as summarized by PulkoMandy:

[...] there will always be people looking for time format settings in the Time preferences instead of Locale. Not just for the DeskBar settings, but also for the system-wide ones. So, we should find a way to have these closer together.

Let's merge the Time and Locale panel into (working title) "Time & Locale" preferences:

• Move Time's "Date and time" and "Time zone" and "Network time" tabs into the Locale prefs.
• Time's "Clock" settings are put directly into the Clock replicant and Deskbar settings:
  1. Put a checkbox "Hide clock" in Deskbar preferences below "Hide application names", rename their BBox label to "Applications and tray.
  2. Add the clock settings currently in the Time prefs' "Clock" tab as menu items in Clock's context menu.
• Remove Locale's "Options" tab and move the "Translate application and folder names..." checkbox from there to the "Formatting" tab above/below the "Use month/day-names..." checkbox.