Remove fragments from TeamsManager

This removes fragments from the TeamsManager components, as it's only used for attaching teams to collections.

This also improves the form by adding required properties and a submit handler to the form, so that empty fields can be highlighted by form validation (previously if you clicked the submit button and hadn't filled in one of the fields nothing happened and there was no feedback).

I tried making the form display either collections or fragments depending on whether a collection=* query parameter was present (i.e. if a collection was specified the form would handle adding teams to fragments of that collection), but it's currently too difficult to ensure that all of a particular collection's fragments are loaded into the redux store so I had to take that out again.

refs #20