Use a "natural" sort order when enumerating the scripts to execute

Right now you have to zero-prefix the script names, for example
0001_Foo.sql
0002_Bar.sql
...
0010_Baz.sql

That's slightly ugly.  Worse, the limit might eventually be reached.

Using a natural sort order lets you name the scripts:
1_Foo.sql
2_Bar.sql
10_Baz.sql
That's a good question, which I hadn't thought of.

Previous default sort: 46 ms.  Proposed natural sort: 60 ms.  Those are the average times for sorting 15 000 incrementing filenames.  I'd describe that as slower but immaterial.