Try loading bundles unspecified in the master file

This makes possible adding bundles just by populating their locale-specific directories - without modifying  the master file, which may not be easy after the product has been deployed and the language packs cannot modify it.

If the locale is specified in the master module, no additional locale forms are tried.  For example, if `{ "fr": true }` is there and the configuration requests `i18n: { locale: "fr-fr" }`, the "fr-fr" bundle is not attempted to load.  This makes the dynamic behaviour not affect the existing master modules with explicitly specified locales, if this change should not affect them.

Bundles are attempted to load on the first access and the success or failure are remembered by `true` or `false` in the master object; not to repeat the loading attempts later again.