Solr search now works!

Tested with Solr 4.2.1 on OSX.
Basic faceted search now working
Use minimum price for group products in price facet
Price range faceting now works
Use setting to confiture facets

This supports range facets specified by "facet queries".
Updated makefile for building Solr indexes
We now require purl>=0.6

As it add some super-handy method for manipulating URLs that uses lists
of query params.  These are used for manipulating Solr URLs.
Add handling of when Solr is down
Add fixture for sample books

Add csv with products
Add images to folder
Fix import to work with Date type attributes
Fix import_product_images to skip and report on images for which there is no product
Modify product attributes fixture to include publication date, author and weight
Merge pull request #635
Include pysolr in demo dependencies
Render hidden fields at the top of the form

To avoid a whitespace issue.
When payment fails, render the payment details page

Not the preview page.  As the preview page can contain a hidden bankcard
form which won't be populated correctly.
Add template block for hiding payment forms
Add Datacash support
Hide header in login/registration page

Was showing a HR with no title.  Looked odd.
Allow shipping methods to have HTML descriptions
Include helpful information in demo templates

Such as testing payment details
Add a few shipping methods
modified the abstract_models.py to get product.is_available_to_buy working properly