Overhaul the i18n functionality to make sure we hit all the appropriate filters for translating text.  This includes 'gettext', 'gettext_with_context', 'ngettext', and 'ngettext_with_context'.

This ticket introduces the hybrid_translate() and hybrid_translated_plural() helper functions to streamline the code a bit.

Also, the filter calls have been moved out of the 'Hybrid' class into the i18n.php file.
Fix so that the title appropriately displays on the posts page when it's not set as the front page.