Fix SOFA config file for CLIs

A few things here:
 - Add variables to the SOFAConfig file for easier integration of SOFA in
external project
 - Export the Sofa libraries properly. This is done by exporting the
library in the postBuildConfig.cmake after it was added. The
preSolution.cmake makes sure that a target file doesn't already exist to
prevent appending an already existing file.
 - Use the library name instead of its location for linking.
 - Add variables for the SOFA external libraries
Merge branch 'SOFAConfig' into bender-SOFA-1.0

* SOFAConfig:
  Fix SOFA config file for CLIs
  Added SOFAConfig.cmake and UseSOFA.cmake so it can be use as external library.