Fixed some bugs

- Graphic bugs : the view wasn't updated well when scrolling and and
deleting a neuron
- Fixed a memory leak when meu was aboutToHide()
- Menu appears now only on right-clicking a neuron
Improved code quality

- Simplifly the elementVectorToMathFunction() and created the namespace
createMathFunction
- Reorganized some comments to respect the 80e-column guideline
- Improved the TestLearningProcess to mesure in a more regular way the
efficiency of the LearningProcess