Allow setting secrets via ENV / Volume mounts

[j-kaplan]

It would be great if we could specify secrets to be exposed to the pod via the environment or through volume mounts.

[radu-matei]

Are we talking already existing secrets or creating new ones?

[j-kaplan]

Existing secrets.

[radu-matei]

Merged #7
Leaving this open as there should also be support for adding secrets as volume mounts.

Please try this, any feedback is appreciated :)