Gas estimation factor

[annamcallister]

Follow on to #508

Discussed with Cheng who confirmed that

• best practice is to explicitly set a gas limit on a transaction rather than use an estimate
• the default factor for firefly is 1.5 - we see no reason why there should be a difference between the projects

We also agreed that it would be ideal for the quickstart to have a higher factor, since we know that

• this is a gas free chain
• even simple contracts can require more than an additional 50% on top of the estimated value
• early success using this out of the box setup is important

(also included some comment fixes to a yaml file)

[hosie]

LGTM