Cache image elements to Clarifai model results

[Martin-Cox]

Each image should retain it's Clarfiai results on a per model basis so that we don't need to repeat requests for images.

[Martin-Cox]

The image/results should be stored on a per-session basis with a (configurable?) limit e.g. 100 images/results. This is so requests are not made unnecessarily for the same image in different tabs and so that reloading a page/navigating to a previously visited page will not need to make more requests.

Chrome storage information can be found here. Note there are limits to what and how much can be saved, so transformation and optimisation of the results may be necessary.