CORE-69: update sbt and docker images to 1.10.7

[davidangb]

Partially supersedes #1526.

Updates sbt to 1.10.7 and updates our scala-sbt docker image to the matching version.

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Have you read CONTRIBUTING.md lately? If not, do that first.

I, the developer opening this PR, do solemnly pinky swear that:

• I've followed the instructions if I've made any changes to the API, especially if they're breaking changes
• I've updated the FISMA documentation if I've made any security-related changes, including auth, encryption, or auditing

In all cases:

• Get two thumbsworth of review and PO signoff if necessary
• Verify all tests go green
• Squash and merge. Make sure your branch deletes; GitHub should do this for you.
• Test this change deployed correctly and works on dev environment after deployment