Allow non sequential flag numbers

We had the problem that the generated condition wasn't correct any more after someone removed one of the flags for a model class that wasn't needed any more. We then had a gap in our flag numbers (1, 2, 4, 5, 6) and our queries didn't return what we expected.

From a purist's point of view I can understand that developers should be aware of the fact that you shouldn't just pick and match your flag numbers but stuff just happens and I prefer my gems being fault tolerant.