Error with primary key name with SqlServerAdapter and specifying schema

Migration:

```php
$this->table('custom_schema.table_name')->create();
```

Generates:
```sql
CREATE TABLE [custom_schema].[table_name] ([id] INT   NOT NULL  IDENTITY(1,1), CONSTRAINT PK_custom_schema.table_name PRIMARY KEY ([id]));
```

This gives the error:
```
Incorrect syntax near '.'.
```

`PK_custom_schema.table_name` needs to be parsed to remove the `.`.