Added User welcome message. Added templates/soc/mail/welcome.html as a template for the message. Also fixed a cyclic import that was about to happen in notifications.py.

# Geo-enabled Sitemap classes.
from django.contrib.gis.sitemaps.georss import GeoRSSSitemap
from django.contrib.gis.sitemaps.kml import KMLSitemap, KMZSitemap