ComputeFstat: allow runtime selection of Fstat-method to use

- Demod methods = {DemodGeneric,DemodOptC,DemodSSE,DemodAltivec}
  Resampling methods = {ResampGeneric}
- allow selection of respective 'best' (guessed) Fstat-Method via
  special names {DemodBest,ResampBest}
- atticed Demod hotloops: SSE_MSC, Autovect, Akos8, non-precalc-SSE
- removed 'useResamp' user-input switches from CFSv2, GCT
- record used Fstat method in log output of CFSv2, GCT
- refs #543