fix PrimaryVertexChecker output

• small fix to properly show close and isolated categories and clone rate. The output looks more reasonable again:

Primary vertices:
REC and MC vertices matched by dz distance
MC PV is reconstructible if at least 4 tracks are reconstructed
MC PV is isolated if dz to closest reconstructible MC PV > 10.00 mm
REC and MC vertices matched by dz distance

All                  :  0.92 ( 22085/ 23891)
Isolated             :  0.95 ( 11727/ 12297)
Close                :  0.89 ( 10358/ 11594)
False rate           :  0.02 (   430/ 22515)
Real false rate      :  0.02 (   430/ 22515)
Clones               :  0.00 (     6/ 22085)

• add a digit in output of PVChecker:

All                  :  0.924 ( 22085/ 23891)
Isolated             :  0.954 ( 11727/ 12297)
Close                :  0.893 ( 10358/ 11594)
False rate           :  0.019 (   430/ 22515)
Real false rate      :  0.019 (   430/ 22515)
Clones               :  0.000 (     6/ 22085)

closes #106 (closed)