Errors in discretized sympde Norm and SemiNorm

[campospinto]

After discretization, the Norm and SemiNorm objects of sympde return wrong values for simple scalar functions.

In particular the following configurations seem to return wrong values:

• Norm of complex-valued function
• Norm of complex-valued FEM field
• SemiNorm of real-valued function
• SemiNorm of complex-valued function
• SemiNorm of complex-valued FEM field

These bugs should be fixed. A test has been added to try and check these configurations: see #11

[campospinto]

For real-valued functions, the error seems to be solved (probably by sympde's PR pyccel/sympde#163).

For complex-valued function, the errors should be solved with sympde's PR pyccel/sympde#133.