Towards dropping GaudiAlgorithm

Dropped not needed references to GaudiAlgorithm

Converted TestRecVertexHolder and CheckPV to functional

Dropped a number of unused algorithm :

• PVRelatorAlg
• BestPVAlg
• BestPVAlg2
• FilterEventList @sstahl @graven @erodrigu can you confirm these can go ? Or point me to whoever can confirm ? Note that I've carefully created on commit per file, so we will be able to revert selectively any file I should not have deleted. Only point is that they would have to be modernied