Updated Vietnamse translation

Signed-off-by: Trần Ngọc Quân <vnwildman@gmail.com>
main: Remove spacing around preferences tabs

With help from Ignacio Casal Quinteiro

https://bugzilla.gnome.org/show_bug.cgi?id=740677
main: Cancel thumbnailing on destroy

Stop thumbnailing when TotemGrilo object is destroyed.
main: Make it possible to pause icon thumbnailing

Using g_thread_pool_set_max_threads() with 0 max threads, to freeze
further processing until we reset the max threads count.
main: Add helper to pause thumbnailing in grilo widget
main: Pause thumbnailing when playback starts
backend: Add track-skip-requested signal

So that the video playback can request skipping tracks.
backend: Fix object type in signal handler

It's a ClutterSwipeAction, not a ClutterTapAction.
backend: Request next track when swiping with 2 fingers

https://bugzilla.gnome.org/show_bug.cgi?id=697896
main: Skip tracks when using 2-finger swipes

https://bugzilla.gnome.org/show_bug.cgi?id=697896
main: Handle "Powerpoint" buttons on remotes

Some remotes, including the Logitech Presenter R800:
http://www.logitech.com/en-us/product/professional-presenter-r800-business
have a number of buttons bound to make it easier to use Powerpoint
presentations.

We bind some of the buttons used on those presenters to functions
in Totem to allow starting/stopping playback and seeking.

https://bugzilla.gnome.org/show_bug.cgi?id=704608
Revert "backend: Request next track when swiping with 2 fingers"

This reverts commit 99dcbf8e9a97c261aa9620e038e5958dc1a9e975.

We'll need to implement our own ClutterGestureAction for this to work.
backend: Remove mention of the browser plugin
main: Keep the controls visible when seeking with the slider

When seeking with the handle, mark the popup as busy so it's not
hidden, remove the business when releasing the slider handle, or
when an error occurs.

https://bugzilla.gnome.org/show_bug.cgi?id=732711