COMP: If a Logic directory exists in a modules directory, the directory will be automatically added.

The process allowing to build the 'Logic' library of a module had been factorized out.
That way the dedicated libray is build and both the QTModule and the regular Module can link against it.

There is not need to add Win32 header file or any configure header.

Using the macro Slicer3_build_module_logic automatically configure a file
of the form ${PROJECT_NAME}Export.h.
For example vtkSlicerTractographyModuleLogicExport.h where
name of the project is 'vtkSlicerTractographyModuleLogic'

Note also that the Logic sub-directory should *NOT* be included in the module
main CMakeLists.txt

As a convention, the module logic library should composed as described below:
  vtkSlicer[MODULE_NAME]ModuleLogic

git-svn-id: http://svn.slicer.org/Slicer4/trunk@11905 3bd1e089-480b-0410-8dfb-8563597acbee