Allowing Filter on Tags

Im trying to enable filter on tags and have the following config:

```
{
"settings": {
"showFilter": true,
"showArrows": true,
"showTags": true
},
"fields": [
{
"name": "System.AreaPath",
"title": "Area",
"filter": true
},
{
"name": "System.IterationPath",
"title": "Iteration",
"filter": true
},
{
"name": "System.Tags",
"title": "Tags",
"filter": true
},
{
"name": "Microsoft.VSTS.Scheduling.Effort",
"title": "Effort"
}
]
}
```

Ive tried with and without `"showTags": true` but to no effect. With `"showTags": true` the tags appear on the cards, but not filterable. Without `"showTags": true` no tags are shown on the card or on the filters.

Any ideas @edtro?

Start by reproducing the configuration in the Query Based Boards Azure DevOps extension with showTags and System.Tags enabled. Verify how tags are displayed on cards and whether they appear in the filter controls; done means tags can be filtered while retaining the existing card display behavior.

Written by the indexing model from the issue text.