add LAGOON_NEW_DEPLOYMENT or similar variable on first build

[tobybellwood]

It would be handy to be able to utilise a variable in the build that could determine if it's the first deployment into a namespace.

This can then be used in pre/post rollout tasks without having to workaround

This could possibly be implemented in the remote-controller

[shreddedbacon]

Moved to remote-controller as this is where this logic will need to live. Basically when the namespace is created, we can inject this variable into the build pod.

For naming:

• LAGOON_NEW_DEPLOYMENT
• LAGOON_FIRST_DEPLOYMENT
• ?