Tidy sandbox settings

* Comment on store-specific settings
* Remove some dead ones
Tidy stores fixture

* Add placeholder images
* Load stores during 'make sandbox'
* Add HTML descriptions
Replace fixture image with kwik-e-mart
Improve store detail page

* Include store image
* Put HTML description under map
Improve store homepage

* Hide group filter when no options
* Remove float to get spacing right
Improve dashboard templates

* Fix bug in group display when no assigned stores
* Add street property to address model to avoid duplication
Patch i18n holes in templates

Fixes #36
Minor improvements to templates

* Add thumbnail dimensions
* Make list store image a link to store page
Move statics into own folder

These need to be namespaced as they all get moved into STATIC_ROOT upon
deployment.
Add HTML flash messages when saving stores
Tidy up utils.py