Set up consistent node versioning in projects

nvm or n (I forget which) is able to run node projects with a version of node that is configured in the project code.

• configure build and watch tasks to run with a consistent version of node specified in the project config
• document (in README) any installation that is needed for this to work properly
• make sure a helpful error message is shown if the above installation has not been done (if applicable)
• should still allow running with the wrong version of node, but warn that it is not the recommended version