Add a view component for tagging, replacing bootstrap-tagsinput

[taylor-steve]

One possible solution for https://github.com/projectblacklight/spotlight/issues/2890

A variation on the code mentioned in #3074 in another attempt to remove the dependency on bootstrap-tagsinput. Supports the same input scheme as bootstrap-tagsinput, but does have a different look and feel.

[taylor-steve]

Looking for feedback on if my changes (the ability to add a new tag on the fly) to the original, good widget that I adapted ruin it. Sometimes I think it makes it a bit unwieldly, but it is functional.

If people think this is okay to use in this way, Alan wanted a demo or a push to stage for final say.

[jcoyne]

Would it be better to use the tag UI that @dnoneill developed for Argo?