Resolve "Room model, service, logic & view"

Closes #19 (closed) #29 (closed) #26 (closed)

Proposed changes

• make http client available
• add room model
• create in-memory-data.service
• add room service & room component
• add room-list component

Contributors

• @tlnz55
• @lmas60

For testing

Copy <app-room-list></app-room-list> & <app-room></app-room> temporary into app.component.html.