give reader users permission to saved searches

also adds permission checks in the templates, basically everyone has those permissions now.

fixes Graylog2/graylog2-web-interface#545
add more permission checks to templates to prevent user confusion

none of the hidden actions could've been executed by the user anyway, because the server would disallow them. just cosmetics, really.

fixes #544
Merge git://github.com/Graylog2/graylog2-web-interface into develop