BUG: Use JsonCppConfig.cmake only if the file is present.

Co-authored-by: Jamie Snape <jamie.snape@kitware.com>
BUG: Scale cannot be negative in optimizer test.
Merge pull request #9 from thewtex/JsonCpp_DIRDefined

BUG: Use JsonCppConfig.cmake only if the file is present.
Merge pull request #10 from thewtex/Scale-sign

BUG: Scale cannot be negative in optimizer test.