Sort order for pipeline build lists doesn't properly handle numbers

The build list sort order was greatly improved by !7681 (merged) but there's still a small issue when sorting items which contain numbers of variable digits.

For instance:

The correct order should be:

rspec 0 20
rspec 1 20
rspec 2 20
rspec 3 20
...
rspec 10 20
rspec 11 20

but instead, the rspec 1X 20 items get sorted above rspec 2 20 because it is a straight alphanumeric sort.

We could instead use a "natural sort" algorithm to get this into a more intuitively correct order. See https://github.com/sourcefrog/natsort/blob/master/natcmp.rb for an example implementation...

Another alternative would be to just pad the build name numbers with 0s (like rspec 01 20, etc.)