chore(dependencies): Reverting Spring Boot 2.2 upgrade (spinnaker#492)

Revert "chore(dependencies): Upgrade Spring Boot to 2.2.1 (spinnaker#468)"
This reverts commit c2b3a74

fix(gce): Hardcode recently unpublished 14.04 source image. This is a…

… backport of spinnaker#471 (spinnaker#476)

fix(buildtool): Set trusty dist for travis (spinnaker#405)

fix(gce): Hardcode Trusty GCE image in halconfig/images.yml (spinnake…

…r#473)

feat(aws): ability to resolve base ami id by name (spinnaker#458)

feat(kustomize): support git/repo artifact in kustomize bake manifest (…

…spinnaker#449)

* feat(kustomize): support git/repo artifact in kustomize bake manifest

* address code review comments

* address code review comments

* address code review comments

chore(dependencies): Autobump korkVersion (spinnaker#455)

fix(bakeManifest): helm --set option (spinnaker#441) (spinnaker#445)

adds an option to toggle between `--set` and `--set-string`. we recently
had to revert a commit which changed `--set-string` to `--set` and
introduced a breaking change. this keeps the default behavior of
`--set-string` but allows users to choose which option they want to use.

fix(bakeManifest): revert to set-string (spinnaker#439)

reverts a change introduced in spinnaker#418 where we went from using
`--set-string` to `--set`. This change caused backwards incompaitble
changes because the parser for `--set` in helm coerces integers into
floats when it injects them into templates. `--set-string` was
introduced to fix this in helm 2.

chore(dependencies): Autobump korkVersion (spinnaker#431)