From ReDecay flag for MCParticle

Adds setter/getter to flag a particle that was produced in the ReDecay part of an event. Uses bit 5 of the already existing bit-field. See LHCBGAUSS-1357

Should go to 2018-patches and master, not sure yet about older versions. Modifications to Gauss and a TupleTool to extract the information will follow. Unless I am mistaken, this only modifies the value of the unsigned integer storing the flags and thus no updates for Run1+Run2 Boole, Moore and Brunel should be necessary to propagate the information.