Improvements of the 'performance' test program

[Nicklas Nordborg]

I will gather a few enhancements to the 'performance' test program under this ticket. Feel free to add more items to the list.

1. Names of raw bioassays should be 0-padded to make them sort correctly. Right now the sort order is: ...#1, ...#10, ...#11, ...., ....#2, .... and so on, which makes it hard to select a specific number of raw bioassays when creating a root bioassay set.