Since it's using `require` to get the localisation strings, check if the error is `MODULE_NOT_FOUND` before moving on – because if it isn't, then there is an unknown error that should be thrown. Thanks @rschamp for the suggestion!
Before we were using glob, which was about to start failing on subdirectories in views (which we started using in `conference`). Instead of searching for `l10n.json`, it seemed more appropriate to instead look for localization by using the configured pages that need to be localized.
The catch there before is meant to just continue if it comes across a file that doesn't exist (in which case the language will default to english). However, it was not specific enough – now, it only catches the error if the file doesn't exist, and throws anything else, preveting a build.
This moves all locale/translation building to a dependency, `scratch-www-intl-loader`, as well as tests associated with it. Also gets rid of the `make translations` step.
1. Load locale strings into `window._messages` in a separate file added to `template.html`, which contains view-specific and general strings
2. Update build-locales to compile separate files
