Removes support for deprectaed SubjectBrowse plugin
Adds basic support for GuestUser plugin

Note that this plugin currently (apparently) causes some issues with
the mobile-json output context and shouldn’t be used until that’s
figured out.
Support for internationalization

Special thanks to @jeau for starting the process and submitting many of
these updates.
Formatting
CSS: Fixes IE Metro snap view
fixes via @greyson
Merge remote-tracking branch 'upstream/master'

Conflicts:
	curatescape/common/header.php
	curatescape/custom.php
	curatescape/error/403.php
	curatescape/error/404.php
	curatescape/items/browse.php
	curatescape/simple-pages/page/show.php
	curatescape/stealth-index.php
	curatescape/tour-builder/tours/browse.php
	curatescape/tour-builder/tours/show.php