Fix "./manage.py fetch_satellites"

Running the command ./manage.py fetch_satellites results in the following error:

(env) kerel@host:~/satnogs/db$ ./manage.py fetch_satellites --help
Traceback (most recent call last):
  File "./manage.py", line 11, in <module>
    execute_from_command_line(sys.argv)
  File "/home/kerel/satnogs/db/env/local/lib/python2.7/site-packages/django/core/management/__init__.py", line 367, in execute_from_command_line
    utility.execute()
  File "/home/kerel/satnogs/db/env/local/lib/python2.7/site-packages/django/core/management/__init__.py", line 359, in execute
    self.fetch_command(subcommand).run_from_argv(self.argv)
  File "/home/kerel/satnogs/db/env/local/lib/python2.7/site-packages/django/core/management/__init__.py", line 208, in fetch_command
    klass = load_command_class(app_name, subcommand)
  File "/home/kerel/satnogs/db/env/local/lib/python2.7/site-packages/django/core/management/__init__.py", line 40, in load_command_class
    module = import_module('%s.management.commands.%s' % (app_name, name))
  File "/usr/lib/python2.7/importlib/__init__.py", line 37, in import_module
    __import__(name)
  File "/home/kerel/satnogs/db/db/base/management/commands/fetch_satellites.py", line 9, in <module>
    class Command(BaseCommand):
  File "/home/kerel/satnogs/db/db/base/management/commands/fetch_satellites.py", line 10, in Command
    option_list = BaseCommand.option_list + (
AttributeError: type object 'BaseCommand' has no attribute 'option_list'

BaseCommand.option_list is deprecated in Django 1.8 and removed in Django 1.10 (source: 1). The update from Django 1.9 to 1.10 was done in fe1768cd736b440659036cff9dc69430987f9adc.