Retrieve entity named keys and entry points

[jacek-casper]

Uses a new global state request type: ItemsByPrefix to retrieve named keys and entry points for addressable entities. Some notes:

• the node currently never creates entry points V2, and their constructor isn't publicly exposed in casper-types, so it's not covered in the unit test here, but we do retrieve their StoredValues

[jacek-casper]

this is now ready for review @zajko @rafal-ch

[zajko]

Uses a new global state request type: ItemsByPrefix to retrieve named keys and entry points for addressable entities. Some notes:

• the node currently never creates entry points V2, and their constructor isn't publicly exposed in casper-types, so it's not covered in the unit test here, but we do retrieve their StoredValues

You could create a fixture that deserializes a json constant to EntryPoint

[jacek-casper]

I'll try to get something added to the node that allows us to create entry points v2 more easily and then I'll open a separate PR to use it @zajko