Adapt_framework: Create "items" presentation component model

[oliverfoster]

All of these components use the same model behaviour

• Narrative
  
  
  
  • update transformations to css3 inline with dropping ie8-ie10
  
  
• Accordion (https://github.com/adaptlearning/adapt-contrib-accordion/pull/85)
• Hotgraphic
  
  
  
  • use notify subviews and itemscollection
  
  

Create a standard presentation component model for them

[oliverfoster]

any objection to me putting this in the core?

core/js/models/itemsModel.js

[moloko]

Could you also deal with #1365 at the same time?