Removal of FilterDesktop

Step 2 (and part of 1) of Rec#358 . FilterDesktop is obsolete and needs to go.

CombineParticles will be removed in a subsequent MR. Then algorithm.py can be removed as well.

Goes with !2259 (merged) Rec!3392 (merged) MooreAnalysis!119 (merged) MooreAnalysis!121 (merged)