Cache.Purge issues

Currently, there are the following issues with the "Purge cache data" button:

1) The Purge operation only copies entries to the cache store, it does not remove the from the cache itself. So the cache remains full. Checked with cache.withFlags(Flag.SKIP_CACHE_LOAD).get() after I performed the Purge operation and still got the entries. The JMX stats also display entries in the cache.

2) The button is available even though the cache is attached to the remote endpoint and hence available to clients. It should only be available after the cache is detached from the endpoint.

3) The confirmation dialog for the operation always says "Purging cache xyCache will passivate all its cache entries." even though there's no cache store defined for the cache. This might lead users to expectations that their data will be stored somewhere. But if there's no cache store, the data will be lost. In this case, it would be better to show a warning that their data will be lost after performing the operation.