Allow keystore command to add / remove an arbitrary number of settings at the time

[nachogiljaldo]

Describe the feature:
The keystore command allows adding/removing settings one at the time. However, when the number of settings grows this can take quite a while.

It would be great if it was possible to add and/or remove more than one setting at the time so only one JVM had to be initialized. That would cut quite a bit the startup time.

cc @jasontedor

[jasontedor]

The remove command already supports removing more than one key per invocation.