Add hello/goodbye events to SSE system, for increased reponsiveness
Add hello/goodbye events to SSE system, for increased reponsiveness

lackac/horizon,stellar/horizon,FredericHeem/go-horizon,masonforest/go-horizon,masonforest/go-horizon,masonforest/horizon,FredericHeem/go-horizon,irisli/horizon,lackac/horizon,stellar/horizon,FredericHeem/go-horizon,masonforest/horizon,nullstyle/go-horizon,nullstyle/go-horizon,stellar/horizon,lackac/horizon,irisli/horizon,masonforest/horizon,irisli/horizon,masonforest/go-horizon,nullstyle/go-horizon