Add ability to import normal python files / modules to notebooks

Please add the ability to import normal python files (called modules in python lingo) in a notebook. Like this:

import my_normal_python_file

my_normal_python_file.my_reusable_function()

This is normal python functionality but it's currently impossible when working with notebooks in fabric. Since we can only create notebooks and not normal python files, we have the option to use:

%run another_notebook

or

notebookutils.notebook.run("another_notebook")

Neither of these alternatives puts the functions inside "another_notebook" in a nice namespace like the regular python import statement does. 

In databricks you can create regular python files and the import statement works as you expect. It would be nice to have the same functionality in fabric.

Please be aware of the distinction between packages and modules. There is already capability to install and import packages, but python packages are cumbersome to work with during heavy development. The import statement combined with regular python files (aka modules) is just right for a lot of use cases.