Omit empty spec.data, and improve integration test coverage

Improve integration test coverage to exercise both negative
paths (various types of invalid SealedSecrets), and new per-key
encryption.

Add `omitempty` to spec.data, fixing an issue when Spec.Data was
`nil` (yay for tests).

Also: bump version of kubecfg used to generate manifest YAML.

Merge pull request bitnami-labs#76 from anguslees/integrationtest

Add integration framework and tests

v0.3.0 release

v0.2.1 release

v0.2.0 release

Merge pull request bitnami-labs#7 from anguslees/master

Updates - RBAC support