Update Node.js version

[maurizi]

The current version of Node is 6:

temperate/src/angular/Dockerfile

Line 1 in 631d6a0

FROM node:6-slim

This version reaches its EOL at the end of April. The next LTS release is 8, but that has an early EOL, so we should probably upgrade directly to 10.

[flibbertigibbet]

We won't be able to upgrade directly to node 10 without also upgrading Angular and rxjs.

This project is on Angular 4. The most recent version of angular-cli with Angular 4 support is 1.7.4, which does not support node 10. Further, rxjs 6+ does not support typescript 2.x. There is an LTS support branch for Angular 6 for angular-cli, so I think we should be able to upgrade to node 10 on upgrading to Angular 6.

The immediate error on only changing the node version for the Docker container is: Error: Cannot find module 'rxjs/add/operator/map'. (See this issue.) This error occurs on upgrading to node 8 as well.

[flibbertigibbet]

Blocked by #263.