Enable the ability to add a sticky note to the patient dashboard

Add a flag field on the patient header (so it is always visible) to allow the care provider to add a short note on the current patient.
When clicking on this note, the field would become editable (something similar to what's done in JIRA itself when renaming the issue title for instance).
This would use the usual 'obs' method, which means that track is being kept anytime this field is updated. When the user edits the field, the previous content observation still exists in the database but is only voided.