GroupComponent helper.

`GroupComponent` helper implements a sync component that collects input from a set of inports and passes the collected tuple to a callback along with the groups and the main outport that it can use to send output. If group information is provided on inports, then input data from matching groups is combined and group information is automatically forwarded to the output along with the callback's response.

Refs https://github.com/noflo/noflo/issues/166