Restructured all the modules

The core module was becoming too large.
By splitting it in  cluster, monitor and tasks it becomes more manageable. It also reflects the documentation structure.

django_q/__init__.py

@@ -1,29 +1,6 @@
-from django_q.models import Task, Schedule
-from django_q.core import async, schedule
+from .tasks import async, schedule, result, fetch
+from .models import Task, Schedule
 
 VERSION = (0, 1, 4)
 
 default_app_config = 'django_q.apps.DjangoQConfig'
-
-
-def result(name):
-    """
-    Returns the result of the named task
-    :type name: str or unicode
-    :param name: the task name
-    :return: the result object of this task
-    :rtype: object or str
-    """
-    return Task.get_result(name)
-
-
-def get_task(name):
-    """
-    Returns the processed task
-    :param name: the task name
-    :type name: str or unicode
-    :return: the full task object
-    :rtype: Task
-    """
-    if Task.objects.filter(name=name).exists():
-        return Task.objects.get(name=name)