Add some error handling and a README, clean up some CSS & JS

This PR adds some rules to the .gitignore file, moves the CSS in the layout template to the main CSS file, adds a function to process the API response when robots are uploaded (and subsequently displays error notifications when the upload fails for whatever reason) and also adds a README file with instructions for getting the system to run locally.

I've tried to follow the style of the code that already exists in the repository but there's a possibility my IDE has changed stuff in the process. I'm happy to fix up these sorts of things if you can point them out with a line comment.