Fixing PhEval post-processing breaking changes

[yaseminbridges]

After implementing the changes to the PhEval post-processing methods, the methods for post-processing the Exomiser need to be refactored to work.

• [ ] Add a new field in config to accept a sort order for scores to be sorted and consequently ranked (either ascending or descending)
• [ ] Alter methods for refactored PhEval post-processing methods - ensuring it still works