COMP: Remove used flags to JsonCpp build.

For:

CMake Warning:
  Manually-specified variables were not used by the project:

      CMAKE_EXE_LINKER_FLAGS
      CMAKE_SHARED_LINKER_FLAGS
COMP: Only add -Wno-unused-local-typedefs for GCC.

Not found on clang 3.3.
BUG: Fix FindJsonCpp.cmake for finding the include directory.

The current version does not find the proper include directory.
Merge pull request #243 from thewtex/build

Build
ENH: Bump SlicerExecutionModel to use updated FindJsonCpp
Merge pull request #244 from aylward/UpdateSlicerExecutionModel

ENH: Bump SlicerExecutionModel to use updated FindJsonCpp
BUG: Fix FindJsonCpp for library location with Visual Studio.

Also bump ParameterSerializer and SlicerExecutionModel so their versions are
updated, too.

Pull from upstream SlicerExecutionModel instead of a fork.

Change-Id: I7e7e792bdaad050dd26c599c537dd32e26e61260