display CreatedAt field in v3 output
display CreatedAt field in v3 output

- Use current droplet's CreatedAt field as the time the app was created
in the v3-app output.

[#158607105]

Signed-off-by: Alex Zhao <ec17dce03b325b5df7bbb0522a847fd834ca508b@pivotal.io>

cloudfoundry/cli,cloudfoundry/cli,cloudfoundry/cli