The current shared cache configuration semantics are non-standard and limiting.

I'd like to shift the set of options and their defaults from:

shared_cache=(chunk=10MB,name=none,reserve=0,size=500MB)

To:

shared_cache=(chunk=10MB,enabled=false,name=shared_cache,reserve=0,size=500MB)

If I make this change, it'll break backward compatibility via the default configuration file. The configuration will be enabled by default in the older version, since it relies on the name field to imply that the shared cache is enabled.