Hotfix/4.5.2

[nsoblath]

New Features

• Adds a dev docker image

Fixes

• Build now works with dripline-cpp as an external dependency. Uses dl-cpp v2.6.2.

Testing

• Builds locally in docker
• Builds on Travis
• TODO: dl-cpp applications print debug text
• TODO: dl-cpp test applications and examples are present

Prior to merging for releases:

• [x] update the project's version in the top-level CMakeLists.txt file
• [x] update the appVersion to be the new container image tag version in chart/Chart.yaml

[laroque]

I think this looks pretty good, pending the merge of dripline-cpp 2.6.2 and successful CI jobs.

[nsoblath]

@laroque I believe this PR is ready now. The GitHub Actions build stuff is new, so you should take a look before we merge.