Update to Cypress 3.5.0

Update to Cypress 3.5.0

Also get around issue with using --env and setting the baseUrl by setting the variables directly in cypress.json. See https://github.com/cypress-io/cypress/issues/2518#issuecomment-547103226

Not entirely consistent locally but tests do usually pass after a retry

Dev notes

• https://docs.cypress.io/guides/guides/environment-variables.html
• https://docs.cypress.io/guides/references/configuration.html#Options