Completions for nested types

[jmbockhorst]

There should be completions for nested types. For example:

type alias Data =
    { prop : String
    }


type alias Model =
    { data : Data
    }


test : Model -> String
test model = model.data.|

model.data. should have completions for the Data type.

[razzeee]

We need to figure out how to get the tree to be stable enough to recommend correctly, when you press Control+Space after a dot.