Samples should be standalone

[steren]

/area build
/kind doc

Keep things simple. Each sample folder should contain all it needs to be followed.

Expected Behavior

Each sample folder should contain all thing necessary to build and deploy.
For example, I expect a Dockerfile in this folder

Actual Behavior

Sample folders depend on a common Dockerfile that expects a certain folder structure and argument: RUN CGO_ENABLED=0 go build ./sample/${SAMPLE}

This prevent to easily re-use the samples and requires developers to adjust the samples to their setup.

[steren]

Also evaluate moving samples to their own repo.
This would allow for a better separation of concerns, improve discoverability and facilitate community contributions

[rgregg]

I'm fixing this as part of the move to knative/docs.

[mattmoor]

samples are moved