Infer type arguments based on the return type

[Victorious3]

This is specifically to address the need for having to call:

var m: &Map(Str, int)
m = map::make(Str, int)

The information is already baked into the return type so it might be possible to infer it using this syntax:

def make -> &Map(type K, type V) {
    // use K and V here
}

m = map::make()

You could also do fancy things like overloading based on the return type:

def function -> type T {
    #if T == int {
        return 20
    } else if T == Str {
        return "Some string"
    } else {
        ...
    }
}

This does make overload resultion harder but it should be possible to implement by using a context type.