Enhancement: A11y improvements for meta attributes

For a11y the html language attribute will be set dynamically <html lang="xx"/>.
For a11y the title will be set automatically following the schema:
sub item (e.G file) - route (e.g All Files) - general name (e.g ownCloud)

https://github.com/owncloud/web/issues/4342
https://github.com/owncloud/web/issues/4338
https://github.com/owncloud/web/pull/4811
