zipkin-ui: improve page rendering time by re-configuring jquery-i18n-properties (#1846)
zipkin-ui: improve page rendering time by re-configuring jquery-i18n-properties (#1846)

By default the `jquery-i18n-properties` plugin appends the current timestamp every time it requests the language `.properties` file, which requires the file to be loaded on every page load and prevents it from being served from cache.

By enabling the [`cache` option](https://github.com/jquery-i18n-properties/jquery-i18n-properties#options), that will no longer happen.

Another factor is the loading of several language files that is attempted. In my case `traces.properties`, `traces_en.properties`, `traces_en_US.properties`. The first one succeeds, the other 2 return a 404. That 404 cannot be cached by the browser.

The `async` option defers the loading of additional files, which should also improve time to render.

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