fix(single-source): mv script outside fpm's purview

[rouson]

This PR addresses several issues with the script that creates single-source-file versions of Inference-Engine examples.
The PR

• Moves the script to a new subdirectory scripts, which fpm doesn't search. This move prevents fpm failures due to code replications.
• Prints diagnostic output in some error conditions.
• Provides sample compile commands instead of attempting to compile the programs.
• Creates two single-source-file programs:
  • concurrent-inferences.F90
  • saturated-mixing-ratio.F90