Translate 'Tatoeba' and uniformize title.

<pagename> - <sitename> is most commonly used and it allows to
know what page the tab/window contains by just looking at the
first characters.

Languages that don’t commonly use Latin characters should be able
to express the site name appropriately in the title. We won’t
loose the English keyword “tatoeba” since it is in the URL already.
Fix broken titles.

Add page title where it was missing,
or append the site name where it was missing.
Merge branch 'master' into titles

Conflicts:
	app/views/sentences_lists/index.ctp
Use a helper function to format page titles.
Merge pull request #479 from Tatoeba/titles

Uniformize/fix page titles and make “Tatoeba” translatable