Add a scope setting for avoiding conflicts in localstorage

[Johan Klokkhammer Helsing]

If the same protocol-domain-port triplet is used by multiple libraries or apps, the keys may conflict with each other. i.e. it's currently probably a bad idea to use generic names like "user".

Perhaps it would make sense to add a store-wide setting for adding a prefix or "name" to keys in order to prevents collisions