Since it is a partial class you can write another partial class to be built into the same class at compile time. Just make sure they are in the same namespace so that they are considered the same class.
This is in c# but demonstrates the same thing.
public partial class SoftwarePlatformEntities
{
public SoftwarePlatformEntities(string nameOrConnectionString)
:base(nameOrConnectionString)
{
}
}
Now you can use the new constructor
using(var ctx = new SoftwarePlatformEntities("metadata=res:// ..."))
{
}