fix LHCBPS-1568: replace try_lexical_cast with try_lexical_convert
fix https://its.cern.ch/jira/browse/LHCBPS-1568 : replace try_lexical_cast with try_lexical_convert for Boost >= 1.56
fix https://its.cern.ch/jira/browse/LHCBPS-1568 : replace try_lexical_cast with try_lexical_convert for Boost >= 1.56