Rebuild routing, sidebar and appbar functionality

Flesh out UI routing and overall navigation with app bar (with buttons) and optional sidebar.

Progress on #3 (closed)

added to epic &1 (closed)

added workflowIn Progress label

changed the description

mentioned in merge request !4 (merged)

added workflowReview Required label and removed workflowIn Progress label

changed milestone to %Sprint 89

added workflowRework label and removed workflowReview Required label

added workflowReview Required label and removed workflowRework label

closed via merge request !4 (merged)

mentioned in commit 23e77585

added workflowDone label and removed workflowReview Required label