Add option files to select centrality in EPOS

Port the merge of branch 'LHCBGAUSS-1615.CentOptionFileEpos' into 'Sim09'

See original merge request !537 (merged) into 'master'

(cherry picked from commit 62643ba0)

• de6a8f8d Add option files to select centrality in EPOS
• 37a97b69 Add python function to set centrality in EPOS
• 98628b9a Deleted specific options replaces with a function