README needs update for how to configure the topic subscription

[deanlinaras]

Both README and INSTALL documentation have references to the old remoteControlPlane.topicSubscription configuration key that i believe is no longer used (being replaced by subscription.pubsubTopic) thus creating a bit confusion as the most basic tutorial won't work.

[Arkessler]

+1 As a new user trying to figure out how to actually implement tasks/actions (which the keptn docs don't help much with), it's incredibly frustrating that the basic hello world in JES doesn't work out of the box. I don't even see subscriptions documented anywhere except in the keptn docs for writing new custom integrations, which I don't believe it is reasonable to expect new users to read.

[huseyinbabal]

Both README and INSTALL documentation have references to the old remoteControlPlane.topicSubscription configuration key that i believe is no longer used (being replaced by subscription.pubsubTopic) thus creating a bit confusion as the most basic tutorial won't work.

I also verify, current README is outdated.