Django 1.4 stopped creating django.wsgi files and the common
practice now for a while has been a wsgi.py since it is actually
python code, and should actually be importable.

Right now someone has to copy and rename the existing file if they
want to use it with a server like gunicorn.

This patch adds a new file in location that is importable via python
and adds a deprecation log to the old one.

This also updates the wsgi generation commands to instead  create
'horizon_wsgi.py' and have the apache conf generation also use that
or the default wsgi file.

Change-Id: I0f8bd16c8973ad23bcd8f73b54584dc69e5aed0c
Closes-Bug: #1763204