Improve error for using DefineMap with a lower-cased type in definition

[ilyavf]

Recently ran into a misused map definition: DefineMap constructor as lower-cased type along with instance of the DefineMap as value, which resulted into an unhelpful error. Lost a lot of time to figure out the misusing:

const Currency = DefineMap.extend({});
const VM = DefineMap.extend({
    currency: {
        type: Currency,                   <<< should be `Type: Currency`
        value: new Currency({})
    }
}) 

The error showing was:

 TypeError: Cannot read property 'definitions' of undefined
    at Function.define.setup (http://localhost:8080/node_modules/can-define/can-define.js:697:32)

which makes sense since it does relate to types.

Expected: a message like: In your define map you should use Type on a property that is an instance of a DefineMap.