views: add feature filters to the catalogue list

A feature filter is something like "on sale", "award winner", "eco-friendly", etc.  Ie it is a boolean switch.  Unlike the other filters I've added so far multiple feature filters can be active at a time.
filters: remove some duplicated code from my BooleanFilters
filters: refactoring to reduce repeated code
filters: add a recently added filter

The filter accepts an integer representing number of days.  Products that were added within the specified number of days will be returned by the filter.  I modified the 'New Products' link on the home page to only show products added within the last 2 months (60 days)
templates: preserve query parameters when navigating between product & category views
templates: fix a dangling "?" that was bugging me in my urls
templates: remove yui3 grids, they were driving me insane
css: fix the product-detail page layout
css: remove the filter list from the document flow when it is empty

This is as opposed to making it invisible but still allowing it to take up whitespace in the document.
filters: whitespace fixes
models: add a (product) Review model
hook up product reviews!
templates: minor improvements to the review page layout
forms: add a name field to the product review form

Initialize this field to be the user's first name (if on file), but allow them to change it.
models: rename the review 'title' field to summary and make the full review optional
css: minor improvements to the product review page layout
views: display the average rating in the product thumbnail
models: oops, add a 'date' field to the Review model
templates: display reviews on the product detail page
views: refactor a view to use an explicit context mapping