Feedback from Joel M4

[joelostblom]

Implement two major two minor

Major:

• [x] #115
• [x] #130

Minor:

• [x] Write about performance API call in reflection
• Should not be able to unselect country -> #130

[srfrew]

My thoughts were

• [x] Implement a short callback clearing or disabling widget selections when a new country is selected
• [x] Set existing charts to greyed out or loading states
• [x] In lieu of updating filtering to handle countries with no data, select 10 countries that are known to work for M4 MVP

[JohnShiuMK]

followed up in #105, done