Add proCosmosReactor for same Container Reactions

[ragiano215]

Adding a new template: proCosmosReactor that is a stripped down derivative of the Propulsion Reactor template for a simpler exposition for:

• demonstrating usage against just Cosmos
• command processing is stripped down to use a single container both for listening and writing events to (the full template requires the monitored and target container to be specified separately, even if you're using the same Container for both)

[CLAassistant]

All committers have signed the CLA.

[bartelink]

template name (and an overview as to the motivation!) should go in the overview - PR title and/or commit when it gets merged should be <60 chars
Also needs to be added to the readme.md (inc putting it in the walkthrough) and the changelog.md

[bartelink]

Thanks for your contribution (and bearing with all the nitpicking)!