Some updates for python3 and last dolfin version (2018)

[cdaversin]

Here are some changes I made hoping to have fenics_ii working with python3 and the last dolfin.
It doesn't work yet, but I share these first changes in case it could be useful.

Note : I have troubles with the ii_assemble function. I'm not sure how the recursive call should work but the assemble function in xii_assembly.py calls the assemble function in reduced_assembler.py which itself call the first one (of xii_assembly), etc.... resulting in a recursion error :

RecursionError: maximum recursion depth exceeded

[MiroK]

Hi Cecille, what is the form you assemble when you get the RecursionError? Unless the form is something crazy 'long' the problem should be that none of the assemblers thinks it can do something
to the form. The way the assemblers work is that they construct some sort of a reduction matrix which is to be multiplied with the ii_assemble of the transformed form.

[cdaversin]

The form I'm trying to assemble is indeed quite long and complex. I am going to try with a simpler one to make sure I get the right behaviour.

[MiroK]

Okay, if it is indeed due to the form then I would definitely like to see it :)