Adds copy constructors to BaseVector and SubVector.
Allows to use DynamicalSystem in Network (Coupling are not permited yet).
Change Network example to match with the previous changes.
+ adds force option to makefiles
Adds functions with pointer parameters
Adds entry to gitignore
Uses function with pointer parameter and correct a bug in f function. In the
previous function, the Sub-DynamicalSystem still watch the same x vector.