R2.2: More discussion & exploration of key findings re. ART impacts with Activity +/- KP

[jessexknight]

Further discussion of the headline finding would be welcome - that the omission of key populations but the inclusion of risk heterogeneity in the generalised population brings about the smallest declines in new HIV infections is notable. Where possible - interrogating which dynamics are most important in the discrepancy between 'Activity (no KP)' and the other three model scenarios would be of interest.