Move the "from openquake import job" line to the bottom

[Muharem Hrnjadovic]

.. of /usr/bin/openquake in order to avoid ugly stack traces when the user just wants to see the version or the help:

ubuntu@ubuntu:/usr/openquake$ openquake --version
Traceback (most recent call last):
  File "/usr/bin/openquake", line 64, in <module>
    from openquake import job
  File "/usr/lib/pymodules/python2.7/openquake/job/__init__.py", line 29, in <module>
    from django.db import transaction
  File "/usr/lib/pymodules/python2.7/django/db/__init__.py", line 14, in <module>
    if not settings.DATABASES:
  File "/usr/lib/pymodules/python2.7/django/utils/functional.py", line 276, in __getattr__
    self._setup()
  File "/usr/lib/pymodules/python2.7/django/conf/__init__.py", line 38, in _setup
    raise ImportError("Settings cannot be imported, because environment variable %s is undefined." % ENVIRONMENT_VARIABLE)
ImportError: Settings cannot be imported, because environment variable DJANGO_SETTINGS_MODULE is undefined.