Tutorial: How to build an Oracle on Substrate (consensus based)

[soulofamachine]

Noticed the off-chain workers implementation was just merged:
paritytech/substrate#1942

An Oracles tutorial, maybe a consensus based one, can build on different SRML functionalities and showcase this new feature. It also has been requested by the community and internal folks a few times.

Synced up with @gautamdhameja 's on his example on inherents : https://github.com/gautamdhameja/substrate-inherents-sample

We'll likely be collaborating on this project shortly. Unless anyone else feels really strongly about doing this - just FYI us :)

[soulofamachine]

closing as this is not urgent / a very large project, not a "tutorial"