Add symptom severity mapping

[mellowgeek]

Symptom inputs need to be mapped to severity and encoded in the message to the backend.

Mapping should be:

• 3 states for Fever: no fever (<98.6); mild (<100.5); fever (>100.6)
• 3 states for Cough: no cough, wet cough, dry cough
• 1 state for breathlessness - (yes/no)

[ivnsch]

Updated/confirmed description:

Memo representation:
Fever: not present | mild | severe
Cough: not present | present(no description) | wet | dry
Breathlessness: not present | present

Where:
Fever not present: Didn't select fever in symptoms OR skipped temp OR temp <98.6
Cough not present: Didn't select cough
Breathlessness not present: Didn't select breathlessness