privacy: confirm before emptying trash or purging temporary files.

Fixes bug #703163
datetime: Implement timezone search with autocompletion

This is first cut at implementing the new timezone dialog design.
Instead of having drop down menus with the city and the continent, we're
now switching to a search entry that has autocompletion.

https://bugzilla.gnome.org/show_bug.cgi?id=694985
datetime: Add API to draw a text bubble on the timezone map

It's currently drawn either west or east of the position marker,
depending where we have more free space.

https://bugzilla.gnome.org/show_bug.cgi?id=694985
datetime: Show information about the selected timezone

... using the text bubble API from the previous commit. We're currently
displaying the time zone abbreviation, UTC offset, city and country
name, and the current time.

https://bugzilla.gnome.org/show_bug.cgi?id=694985
datetime: Mark the time format strings as translatable

... and add translator comments explainings what they do. The RTL
languages are likely going to want to show them in a different order.

We should eventually move to just using GnomeWallClock and/or
g_date_time_format with %c that already have translated the time format
strings. However, in case this doesn't make it in time for 3.10, mark
the current strings in g-c-c as translatable to get some translation
coverage.

https://bugzilla.gnome.org/show_bug.cgi?id=694985