Hook up event series and events in the sidebar

Building on the work in https://github.com/CUL-DigitalServices/grasshopper-ui/pull/37 the event series and events should be fetched for courses and parts selected in the pickers.

The back-end work for this hasn't been merged yet so the https://github.com/fronteerio/grasshopper/tree/groups-events-series branch should be used for development.
I've created a [new issue](https://github.com/CUL-DigitalServices/grasshopper-ui/issues/52) for this, since this needs some pluralisation.