gen.py does not support properties that are List and have no Resources

I can try fixing it, I just need some guidance.

For example:

```
"AWS::LakeFormation::DataLakeSettings.Admins": {
"Type": "List",
"Required": false,
"Documentation": "http://docs.aws.amazon.com/AWSCloudFormation/latest/UserGuide/aws-properties-lakeformation-datalakesettings-admins.html",
"ItemType": "DataLakePrincipal",
"UpdateType": "Mutable"
}

"AWS::LakeFormation::DataLakeSettings": {
"Documentation": "http://docs.aws.amazon.com/AWSCloudFormation/latest/UserGuide/aws-resource-lakeformation-datalakesettings.html",
"Properties": {
"Admins": {
"Type": "Admins",
"Required": false,
"Documentation": "http://docs.aws.amazon.com/AWSCloudFormation/latest/UserGuide/aws-resource-lakeformation-datalakesettings.html#cfn-lakeformation-datalakesettings-admins",
"UpdateType": "Mutable"
}
}
},

```

Has the output:
```
class Admins(AWSProperty):
props = {
}

class DataLakeSettings(AWSObject):
resource_type = "AWS::LakeFormation::DataLakeSettings"

props = {
'Admins': (Admins, False),
}
```

When I think it should be:

```
class DataLakeSettings(AWSObject):
resource_type = "AWS::LakeFormation::DataLakeSettings"

props = {
'Admins': ([DataLakePrincipal], False),
}
```