Entries in config without entry in initializer causes cryptic error

[vputz]

Entries in a configuration without a specific entry in the initializer cause a cryptic error (need to get example). There should be a more obvious error when this happens.

Alternately, we could enable a default initializer of "dict", such that

A = { b="c" }

Would set the value of A as dict(b="c") which is probably more like Integrant's behaviour (verify).