Fixed multiple import errors in Jupyter

@Tyagov

Currently, when running a Jupyter notebook using some types of imports leads to errors. With this fix the following ways to import things are working:

import string                  # worked before fix
import string as s             # worked before fix
from string import ascii_lowercase             # worked before fix
from string import ascii_lowercase, ascii_uppercase, digits           # fixed - used to import only the first thing
from string import ascii_lowercase as a, ascii_uppercase as b         # fixed - used to give "Error at Server Side"
from string import *                                                  # fixed - used to give "Error at Server Side"
from string import Template                                           # works

This was happening because after executing every cell the code would move between SlapOS nodes and lose the imported modules/classes/stuff. This was partially fixed before, but this fix should cover all use cases. I have also added tests for these cases in testExecuteJupyter...