[FIX] Fixed mock_ErrorFunction class to fit with the new version of code. Fixed the harmonic oscillator example.

Tmp

See merge request bes0030/lib4neuro!1

moldyn/lib4neuro#24
moldyn/lib4neuro#28

This reverts commit a152bf0d.

[NEW] [DEL] Removed main.cpp and 'test_cases' executable and created dev_sandbox.cpp and 'dev_sandbox' target instead.

This reverts commit a3520fa1.

This reverts commit c50fa350.

[FIX] Removed dependency on RandomSolution header. Removed unnecessary calls to .get() method from smart pointers.

[ENH] [FIX] Added default values for BUILD_* local variables. Removed header from the list of lib4neuro source files.