PulsarCrossCorr_v2: switched associated time to midpoint of SFT
HierarchSearchGCT: fixed potential problem in SignalOnly handling

- number of IFOs derived from total catalog instead of per-segment
  catalog, which could lead to errors in CreateFstatInput() when
  number of IFOs in a segment is less than for others
- refs #1531
HierarchSearchGCT: small fix in handling of 2-column segment-lists

- if 2-column segment list given, don't try to check number of SFTs loaded
- refs #1531
HierarchSearchGCT: removed defunct 'useWholeSFTs' option

- this option is incompatible with the new-API Fstat functions
- refs #1531
HierarchSearchGCT: of SFT frequency-range determination

- GCT code uses *mid-time* to generate its template bank, not *ref-time*
  as a consequence the template bank will potentially be 'larger' (covering
  more physical templates than requested). Another side-effect is therefore
  that the required SFT frequency-band is based on this (larger) range
  instead of the physically-expected one ...
- refs #1531