Remove not needed import from synapse clustering module

The sets module is deprecated from Python 2.6 on. Use set instead.
Remove not needed imports from annotation clustering module

This is just to make the code a bit cleaner.
Upgrade to Django 1.6

* The TransactionMiddleware is deprecated and replaced by the ATOMIC_REQUESTS
  field in the database configuration. This is basically the same, but there are
  two differences: 1. one cannot switch between commit and autocommit within a
  view anymore (CATMAID didn't make use of this) and 2. ATOMIC_REQUESTS only
  applies to views. TransactionMiddleware applied to all middleware classes
  coming after it in the list (CATMAID didn't make use of this,
  TransactionMiddleware was last).
* Updated the manage.py code to the currently recommended format.
* Updated django-taggit to its recent version to be compatible with Django 1.6.
  This application started using South. Therefore, the first migration of them
  have to be faked (see below).
* Update django-guardion to version 1.1.1, because it didn't support Django
  1.6 before.
* Update django-adminplus to version 0.2.1, because it didn't support Django
  1.6 before.
* Update django-devserver to git version after 0.7.0, because it caused an
  infinite recursion in Django 1.6 before:
  https://code.djangoproject.com/ticket/21348
* Update South to version 0.8.4, because it didn't fully support Django 1.6
  before.
* Update django-celery to version 3.1.1 and celery to version 3.1.7, because
  they didn't fully support Django 1.6 before.

To migrate the database, you have to do the following:

  1. Activate the virtualenv
  2. ./manage.py syncdb
  3. ./manage.py migrate taggit --fake 0001
  4. ./manage.py migrate

Your settings.py file needs a new setting called ALLOWED_HOSTS. Please add it
manually or re-run the create_configuration.py script. It is a list of allowed
hosts that a tested agains a request's Host header. More Info can be found here:
https://docs.djangoproject.com/en/1.6/ref/settings/#std:setting-ALLOWED_HOSTS

  ALLOWED_HOSTS = ['CATMAID_SERVERNAME']

If you see the error 'No module named five' when calling manage.py, uninstall
and then install again django-celery:

 pip uninstall django-celery
 pip install django-celery