Configure mass indexing operations on cache start-up

Allow the user to define some configuration to trigger mass indexing operations (e.g.: purge or reindex) when the cache starts.

These actions are usually needed to keep data and indexes aligned (consistent).

For instance if the data is persisted and indexes not or if the index persisted directory is always wiped out, the user might want to always trigger reindex on startup.

Similarly, if the data is non persisted and the indexes are persisted, the user might want to always trigger a purge on startup.

We can introduce an Enum such as startup-mode=NONE|REINDEX|PURGE.

It would allow us to extend it to some automatic mode startup-mode=AUTO where we can check for instance if a cache-store is configured.