Add asset ui tool

[smcalilly]

Overview

This PR contains all the code we developed for the GIS asset feature. We've been submitting PR's against this branch, so all the code has been reviewed.

Based on this architecture outline that @hancush and I came up with: https://gist.github.com/smcalilly/4d1bc364d7c241b0da1bbab305cd1f98

Testing Instructions

• visit review app: https://ccfp-asset-d-asset-ui-g1nsd9jw.herokuapp.com/
• test user credentials are named "ccfp-asset-dashboard test user" in the lastpass shared folder
• to use the asset ui: create a phase -> go to the phase -> add an asset

[smcalilly]

At a high level, my thoughts on the Python are that I think it would be easier to set up endpoints to list GIS assets and create local copies with Django REST Framework than to roll our own implementation, as you have here.

Just remembered another reason I didn't do pure json endpoints @hancush. It's my understanding that for efficiency with a CDN and caching, serving HTML is more efficient? So I was trying to serve the search results the old fashioned way with query string params in the URL rather than some ajax requests that may or may not get the benefit of a CDN?