Allow L0/Hlt1/Hlt2 tools used by TisTosParticleTagger to have different TOS fractions

Adapt TisTosParticleTagger so that (at least in Run 2...unclear if the 'split Hlt' test in TisTosParticleTagger actually works...) different TOS fractions can be set for L0/Hlt1/Hlt2.

Coupled with setting TOSFracMuon to zero in !170 (merged) this should "fix" the muon TISTOS bug described in https://its.cern.ch/jira/browse/LHCBPS-1702 and https://its.cern.ch/jira/browse/LHCBPS-1746 without causing problems for L0 or Hlt1 TISTOSing.

See also: Analysis!158 (merged)