Bug 34055: Add API client class to get items

Bug 34055: Add API client class to get items

This patch add a new item-api-client.js API client to fetch items using
our /items REST API endpoint.

Test plan:
Add the following two lines to one of the existing Vue component (in
data() for instance) and hit the view that is using it.
  let client = APIClient.item
  client.items.getAll().then((items) => console.log(items))
Notice that you see all the items in the console.

Sponsored-by: BULAC - http://www.bulac.fr/
Signed-off-by: Matt Blenkinsop <matt.blenkinsop@ptfs-europe.com>
Was failing the pretty test, fixed with yarn pretty
Signed-off-by: Chris Cormack <chris@bigballofwax.co.nz>
Signed-off-by: Tomas Cohen Arazi <tomascohen@theke.io>