Better CI tests of the generated project

[nietaki]

This is basically groundwork for adding ecto to the generator, but should be helpful to keep raxx.kit correct.

I might merge it into my master even if it doesn't get merged here, to unblock myself on the ecto front.

Side features:

• fixed a bug in the generator
• added .formatter.exs to the generated project
• separated the container deps and _build directories from the local ones so that you can go back and forth between developing using docker and locally without build artifacts conflicts (!) in the generated project
• fixed failing tests in the generated project
• formatted the generated code so it's a bit closer to the standard.

[CrowdHailer]

Good descriptive commit messages :-p

[nietaki]

I was hoping you'd squash them anyways :D

If you're happy with it, can you merge it when you're near a computer? It'll make our forks diverge less while I work on other stuff :)