Improved error wrapping and add support for object alias

[jon-walton]

Hi,

I needed object aliases so this PR adds that. It works the same as described in concept.md. It also adds some improvements to the error wrapping that helped debugging my deployment

I did initially set the k8s config to be keyvaultobjectaliases until I saw concept.md, let me know if you want it renamed.

fixes #51
fixes #66

[msftclas]

All CLA requirements met.

[ritazh]

Thanks for your contribution @jon-walton 🎉 Will review this PR shortly.

[ritazh]

I did initially set the k8s config to be keyvaultobjectaliases until I saw concept.md, let me know if you want it renamed.

I think keyvaultobjectaliases is better as it is more consistent with other configs for each key vault object. Let's update this as concept.md is a bit out of date. Thanks @jon-walton!

[jon-walton]

thanks @ritazh , I've pushed a new commit containing your feedback