BUG: Use upstream SlicerExecutionModel.

This brings in improvements for Visual Studio finding the JsonCpp library.

Upstream SlicerExecution saw a rename of "parameterstorestore" to
"deserialize" and fix code accordingly.

Change-Id: I6e3b8bdbfd13a137a227261ba3666cfa0c408886
Merge pull request #251 from thewtex/windows-build

BUG: Use upstream SlicerExecutionModel.