Adds to Melange a tags framework based on taggable-mixin. The taggable-mixin allowed only tag per Datastore model. This is extended framework allows any arbitrary number of tags per Datastore model. Also, now one can define different models for different Tag types which are all inherited from the base Tag model provided by taggable-mixin. The GHOPTask model makes use of 2 tags per model, one for difficulty and the other for task_type, both using the tags framework. Reviewed by: Paweł Sołyga

import datetime
from django.core.management.base import NoArgsCommand

class Command(NoArgsCommand):
    help = "Can be run as a cronjob or directly to clean out old data from the database (only expired sessions at the moment)."

    def handle_noargs(self, **options):
        from django.db import transaction
        from django.contrib.sessions.models import Session
        Session.objects.filter(expire_date__lt=datetime.datetime.now()).delete()
        transaction.commit_unless_managed()