Review system: new key binding 'E', and modification to 'Q'.

'Q' goes to adjacent section when at an end node, if possible.
'E' selects the next segment for review, if any left.
Merge branch 'master' of github.com:acardona/CATMAID
Add ImageJ based tiling script
Add documentation to use Nginx and Gevent as web and WSGI servers
Add missing slash in Nginx documentation
Importer: fix bug that caused an empty group permission table

This bug was triggered only on databases where no projects no
projects already were linked to permissions. This is the case
on an empty database, therefore, in a new instance.
Importer: display image bases in red if they are not accessible via HTTP

The confirmation dialog of the importer now shows whether an image base
is accessible via HTTP. The image base is marked red if not and it is
marked green if it can be accessed.
Importer: fix typos
Importer: mark group permission setting as not required
Importer: fix small bug in confirmation template
Importer: fix bug that could break HTTP accessibility test for stacks
Importer: use correct file extension for HTTP accessibility test
Importer: add option to select user permissions
Importer: only use color in HTTP test output if test fails
Use default template context processors of Django

Template context processors provide templates with a basic context like
the path of static files. Up to now the default processors were not (!)
used. That confused some Django applications like django-guardian which
couldn't refer to some static files because of this. This commits
ensures that Django's default context processors are in use and allows
to easily add custom ones.

Additionally, an old and not used custom template context processor was
removed. Now there are only the defaults processors in use.
Add a wsgi.py file, which is useful for using gunicorn

Now that this file is present in the respository, you can
use gunicorn for CATMAID's django backend with:

  cd ~/catmaid/django/projects
  gunicorn -b 127.0.0.1:8020 mysite.wsgi:application
Change requests from POST to GET for methods where the POST arguments are never read.
This was needed to make uWSGI work without buffering POST data.
Add documentation on how to let Nginx serve Django's static files
Initial steps for switching to using South for migrations

These initial steps are:

 - Adding 'south' to INSTALLED_APPS
 - Making sure that South knows that our custom database
   adaptor is really just postgresql_psycopg2
 - Add some introspection rules for Integer3DField and
   Double3DField
Move the custom fields into fields.py