[#1251] Show message if there're no views created for a resource yet

It might be because it's still being loaded into the DataStore, or because
there's no views. Maybe we should explain these possibilities?
[#1251] support ckanext-viewhelper filters

for reclinepreview backed extensions. Fixes
https://github.com/ckan/ckanext-dashboard/issues/11
[#1251] Fix jshint issues on preview_recline.js
[#1251] Fix problem when calling resource_views_list without a resource

It would've been better to use `resource.has_views`, as this is the intent of
that variable, but unfortunately that's not possible here.
[#1251] Fix test that makes sure we remove recline_preview after CKAN 2.3
[#1251] Upgrade ReclineJS to fa1e4d3

This fixes #1636 and allow us to remove the recline's resource views from
iframes later, if we want to.

The CKAN.js version used is 0dad7d.
[#1251] Bring resource_preview with Recline.MultiView back

I've named it Data Explorer, as it's more self-explanatory than "Recline
Preview". It works the same way as it used to work, and the plugin is still
named "recline_preview" (might be good to change its name as well).
[#1251] Upgrade Recline to fix filters' support

This was fixed in https://github.com/okfn/recline/issues/425
bringing @marks:1251-resource-view fork up to date with @ckan:1251-resource-view
bringing @marks:1251-resource-view fork up to date with @ckan:1251-resource-view