ENH: Improve how libraries are exported in ParameterSerializerConfig.cmake.
ENH: Improve the logic for including the JsonCppTargets.cmake file.

Weird things could happen if JsonCpp was installed.
BUG: Use a project specific variable for relocatable ParameterSerializerConfig.cmake.
BUG: Add guard against double include of ParameterSerializerTargets.cmake.
Merge remote-tracking branch 'origin/ExportTargets'
BUG: Add missing interface export macros.