make fields selection survive pagination and link sharing

a list of the selected fields is now transported through the controller
in addition the query fragment is used to select the shown fields to allow sharing the url directly

only direct searches are preserved right now, the handling of saved searches, new searches, resetting the field list, CSV exports etc need more work

issue #610
add missing javascript library

issue #610
fix stub selenium test

issue #610
Merge git://github.com/Graylog2/graylog2-web-interface into develop