Frankenstein refit settings

The refit was originally meant for cleaner true 4-momenta.  Re-purpose
this to treat mis-id'd intermediate particles (D/Λc/etc → Ds).  So
currently change the refit setup as follows:

  - Mother: keep consistent with truth; the event did pass event
    selection, so LHCb thought it was a Bs.
  - Daughter1: first daughter is an intermediate state, so misid is
    complicated, not a simple misassignment of mass.  LHCb refits
    respective 4-momenta.  Emulate this by refitting with Ds mass
    constraints.
  - Daughter2: bachelor particle; simple misid here.  Keep consistent
    with truth, handled later as LHCb would: assign wrong mass keeping
    3-momentum unaltered.

NB: This is experimental and gives biased mass resolution (in favour of
LHCb reco).  For plots, see (Bd → DK, Λb → ΛcK, etc):
[[notmuch:id:20140129132708.GA3366@kuru.dyndns-at-home.com]]
Merge branch 'local' of github.com:suvayu/B2DXFitters into local

* 'local' of github.com:suvayu/B2DXFitters:
  Add dumped variables (for debugging) to plot