Add itemProperties, itemPropertiesByType and itemPropertiesByIds

[nf-s]

Add itemProperties, itemPropertiesByType and itemPropertiesByIds

Fixes #1052 #5631 #5155 #1408 TerriaJS/nationalmap#1129

• Add itemProperties, itemPropertiesByType and itemPropertiesByIds to GroupTraits and ReferenceTraits.
  • Properties set override strata
  • Item properties will be set in the following order (highest to lowest priority) itemPropertiesByIds, itemPropertiesByType, itemProperties.
  • If a parent group has itemProperties, itemPropertiesByType or itemPropertiesByIds - then child groups will have these values copied to underride when the parent group is loaded
  • Similarly with references.
• All dynamic groups (eg WebMapServiceCatalogGroup) will create members and set definition strata (instead of underride)

New docs

These are a bit rough

• traits-in-depth.md
• strata-examples.md

Background

For the SIP dataset styling issue (in NationalMap) - I’ve been looking into fleshing out itemProperties so I can attach custom styling to each dataset.
The SIP datasets are harvested from CKAN (data.gov.au) - so we can’t use itemProperties in its current form.

Test me

A bunch of CSVs loaded from CKAN - with overridden styles

http://ci.terria.io/item-props/#clean&https://gist.githubusercontent.com/nf-s/67a545b72eef135a9d4903e2a65b9d9b/raw/02fcfcabfc37ad6eedb2908aa0c52ee39bcf6c0c/item-props-by-id.json&share=s-aAu23kmvBQxDNGwoVU3zQxjiGry

Example

https://gist.githubusercontent.com/nf-s/67a545b72eef135a9d4903e2a65b9d9b/raw/02fcfcabfc37ad6eedb2908aa0c52ee39bcf6c0c/item-props-by-id.json

"catalog": [
    {
      "type": "ckan-group",
      "name": "Data.gov.au",
      "url": "https://data.gov.au",
      "itemPropertiesByIds": [
        {
          "ids": ["6TbYz2Jj/01809262-b20a-4fa2-96d2-73114722f364/aa8d7eea-9eed-42e5-a322-1abee690c49a"],
          "itemProperties": {
            "activeStyle": "",
            "defaultStyle": {
              "color": {
                "nullColor": "#F2F3F4"
              }
            }
          }
        }

Checklist

• There are unit tests to verify my changes are correct or unit tests aren't applicable (if so, write quick reason why unit tests don't exist)
• I've updated relevant documentation in doc/.
• I've updated CHANGES.md with what I changed.
• I've provided instructions in the PR description on how to test this PR.

[tephenavies]

This is really good! I've wanted something like this for a while.