Clean code to generate mesh

Add comments.
Move a list to a dict to store info about each direction.
Rearrange imports
Move boundary conditions to a dict

A boundary condition is now a dictionary
taht contains a type and a value (numpy array).

Clean the code, add some comments.

Change the way to open a file without having to close it.
Remove useless import of scipy
Add class BoundaryCondition.

The class is called inside the class BoundaryConditions.
A BoundaryCondition object is defined by its type and
an array containing the values along the boundary.
Adapt code with new definition of bound conditions
Correct small typo
Import  class Matrix instead of *
Adapt code for bound. cond. in a dict

The 4 boundary conditions are now stored in a dictionary.
Add a lot of changes, not running

I wanted to push a maximum of the code from main to Solver.
Code does not seem to run right now.
WIP
Fix all the bugs in pyIBM amd make more modular

New class Domain: a Domain contains a Mesh and possibly a Body.
Push a maximum into methods of the different classes.
Still have to imporve the quality of the code.
Remove unecessary info in _infoFlow of example cylinder
Write solution every 100 ites
Remove examples from gitignore
Update the body coordinates file
Add arguments to parser an update the post-processing scritp
Adapt cleaning script with parser
Adapt script to parser