Drupal 8 initial port

I had to port this module to be used on a Drupal 8 site connecting to ISGweb for iMIS.
I implemented some improvements over the D7 version like altering the SOAP call methods to better process the response data. Since the iMIS stored procedures returns data in different formats: some times just an integer, others a string and most of the time a XML.

Also I implemented three custom hooks for reacting to different parts of the process, specifically:

• Drupal account creation: so you can map any custom Drupal profile field with the data coming from iMIS.
• iMIS account creation: same as above, but allows you to define custom data to save on the iMIS profile.
• iMIS account post creation: This can be used for executing any custom process after the account is created..

There are some things that aren't fully implemented like giving the alternative of replacing the Drupal registration, user profile and password reset pages with iMIS iframes, however I think the current status makes a good candidate for an alpha or beta version.

The module structure changed a lot, I'm attaching a zip in case you want to review the code, and if you agree I want to ask you for permission to maintain the D8 branch of this module in order to apply future patches/ improvements.