Feature/add assets search

I have added an assets search function.

Note: The version will need bumping.

When a project upgrades to this new version they will need to run a rake task included with this pull request:

rake noodall-ui:update_keywords

Noodall::Search relies on keywords, and before the upgrade an asset did not have searchable_keys hence no keywords.

Related ticket: http://cutlets.ofbeef.co.uk/issues/16978