Use current Sentry browser package and forward errorId into eventId
Fix up errorInfo reference
Put Sentry on the window object for GUI to use
Remove unneeded reference to old style Raven and raven-js
Move Sentry webpack config into production only
Add GA tracker ID to window
Allows scratch-gui to use same GA id
Move the rest of the configuration into template-config.js. This way the options are explicitly in the same namespace so we won't be surprised when we add a variable with the same name as an html-webpack-plugin option.
Rename template extension to ejs for syntax-coloring purposes.
