Common drop-down for instance specific actions

Removed the hard-coded URLs and constructed URLs dynamically with the
project URL as the base, as the URL scheming varies across different sites

* horizon/static/horizon/js/horizon.forms.js
  + Remove actions column only in Jio Servers page
  + Fixed css of caret icon to be aligned in centre

* horizon/static/horizon/js/horizon.tables.js
  + Removed the button group HTML from here...

* horizon/templates/horizon/_scripts.html
  + ...and placed that here, to let the django template engine parse it
and inject the dynamically generated project URL specific to the
respective sites.

Implements: blueprint dashboard-ui-t1
Merge branch 'jio_dashboard' of https://github.com/JioCloud/horizon into jio_dashboard