Add NaNHelper utility

See merge request !105

Use NaNHelper to handle bad data output

Use NaNHelper to handle bad data.

The aim of this helper is to allow to print signaling NaN.
This should help to debug uninitialized matrices of vectors values
while printing them.

Add missing tests for ASTNodeBuiltinFunctionExpressionBuilder

See merge request !104

On the way, fixed arguments resulting from a function call of types
R^d or R^dxd

Also remove the treatment of tuple of function arguments, since this
kind of argument cannot be defined in the language (by now?).

Set AssertError to inherit from std::runtime_error

See merge request !103

One now has to write `v = zero` instead of `v = 0`.
A `fill` function is added but it is unclear if it should be kept.

The main interest is that one can now check more precisely the type of
raised errors in unit tests

Fix issue #18

Closes #18

See merge request !102

++ and -- operators are now forbidden in function definitions.
This is the correct behavior for mathematical functions

- concerning function arguments, it was already not supported but
  resulted in a crash
- with regard to outer variables, the behavior is changed since now
  these cannot be modified anymore while calling the
  function. (observe these external parameters can still be modified
  outside of the function definition itself)

Initialize arrays types with invalid data (non Release mode)

See merge request !101

This concerns Array, Table, TinyVector and TinyMatrix by now.

Add handling of flat boundaries made of faces

See merge request !100