Convert project tagging to use multiple selects

[agjohnson]

Convert project tagging to use multiple selects from SUI.

Make project tags field a multiselect sort of field. UI should allow for user typing in a tag, selecting the tag if it exists, or creating a new tag if it doesn't exist. Tags should appear as a horizontal list of labels.

https://semantic-ui.com/modules/dropdown.html#tagging-and-user-additions