Make it easier to define files to include/exclude from offlining

[marco-c]

We do support defining files to include/exclude from offlining, but the node-glob language isn't really easy to use compared to, say, https://github.com/gulpjs/vinyl-fs.

This brought me to write https://github.com/marco-c/gulp-serviceworker to easily integrate Oghliner into Telegram (the web version), but it shouldn't be required.