Kubernetes support for dev environments

[SabreCat]

Continuation of #6965. @ksonney, if you would like to resume work there, just say the word!

Changes

This enhances the existing docker support by adding the needed files to use kubernetes as an upstream cloud controller. This has been tested against AWS, but should be easily adapted to other cloud providers.

From an admin perspective, this starts work on being able to scale habitrpg horizontally. At the moment, it provides support for a persistent mongodb, and one or more web front end containers. Future plans for this include scaling mongodb horizontally, and then cross-region replication (that last one is the tricky one).

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UUID: 4406436b-b20d-4bde-b4c7-af2fed26f90e

[SabreCat]

Requesting review from @TheHollidayInn as he has been working on containerized builds for Habit lately.

@khipkin, do the changes in my latest commit sufficiently address your comments from the other PR? I will need to try to get this working to include sample success output, but I think that's the only piece I haven't explicitly covered.

[ksonney]

I will be adding to it when I have the chance, sadly my day job has been eating all my free time to contribute of late. I will do a review as well, if that's OK.

[ksonney]

Documentation updates look good to me!

[SabreCat]

I'm sorry you ended up waiting so long over this, but @ksonney, thank you for your contribution! I've awarded you Blacksmith tier 1 for your help.

[ksonney]

Better late and "correct" than not at all. Thank you!