ENH: added new objective functions

- flowRate: volume flow-rate through given patches
- flowRatePartition: distribution of the inlet flow-rate to certain
  outlet patches, with given percentages
- uniformityPatch: uniformity of the velocity field at given (outlet) patches,
  expressed as (half) the variance of the velocity field
- uniformityCellZone: same as uniformityPatch, but defined over
  cellZones
- powerDissipation: the fluid power dissipation taking place within
  given cellZones. In the absence of viscous stress at the "inlets" and
  "outlets" of the cellZones, this corresponds to the volume flow-rate
  weighted total pressure losses through the cellZones

ENH: updated nutSqr so it can be used with adjointkOmegaSST too