ENH: Use Slicer/ParameterSerializer and update to HEAD.

The upstream repository location is now github.com/Slicer/ParameterSerializer.

Also update the ExternalProject version to latest HEAD which contains
the latest fixes for Slicer.
BUG: CXX_FLAGS was not propogating fPIC option due to var name error
BUG: IJ article code (itkGeneralizedDistanceTransformImageFilter) invalid
Merge pull request #288 from aylward/DashboardErrors

Dashboard errors
WARN: GeneralizedDistance...unused pragma, shadowed, uninit.
BUG: Preserve default CXX args when adding args
ENH: Explicitly indicate support for boost 1.54
Merge pull request #289 from aylward/DashboardErrors

WARN: GeneralizedDistance...unused pragma, shadowed, uninit.
ENH: Refactored code for FFT filtering
Merge pull request #290 from aylward/FFTTubes

ENH: Refactored code for FFT filtering
BUG: Boost should use shared libs.  Removed unused typedefs and vars.
WARN: Unused typedef warnings
WARN: Removed unused typedefs
Merge pull request #291 from aylward/UbuntuBoostSharedLibs

Ubuntu boost shared libs
Merge pull request #292 from thewtex/ParameterSerializerSlicer

ENH: Use Slicer/ParameterSerializer and update to HEAD.
ENH: Fixed FFT (pads and handled non-zero indexes)
BUG: Fixed FFTGaussianDeriv - must perform FFT on gauss derivs
Merge pull request #293 from aylward/FFT

Fft
BUG: FFT output type defaults to depending on input type. Needs conversion.
Merge pull request #294 from aylward/FFT

BUG: FFT output type defaults to depending on input type. Needs conversi...