Fixed #2871 Adjust product/item prices based on the tax rate differences for inclusive tax shops

Product price adjustments should occur when inclusive taxes are enabled and the applied tax rate differs from the base tax rate. The price adjustments should occur in proportion to the difference between the applied tax rate and the base tax rate: (price / (1 + (basetaxrate - appliedtaxrate) )
Fixed #2864 Moved js-on body class behavior from an API tag to the ShoppCheckoutPage controller
Fixed #2884 Corrected smart collection load option handling
Fixed Also Bought for product pages and added WP cache support
#2871 Fixed tax total when location changes change tax rates
#2871 Corrected product 'not taxed' option handling for EU-RoW tax baleeted pricing code
Merge branch '1.3.x'
Fixed #1995 Added discount support for PayPal Standard subscriptions

Discounts on subscriptions are not straightforward since it is unclear whether to add the discount to the ongoing subscription price, or the introductory trial offer only. By default, Shopp will apply the discount to the ongoing subscription price. Filtering the shopp_paypalstandard_discount_trials to return boolean true will apply the discounts to the trial price instead.
Fixed #2892 Implemented ShoppDBInterface

Refactored all of the mysql_* calls to load the appropriate ShoppDBInterface engine class (for mysqli extension or the original mysql extension).

This should correct both #2892 and #2843
Merge branch '1.3.x'
Fix for #2900

The original if statement would add the scrollable area incorrectly.
Fixed connection detection to not require WP 3.9
Fixed #2897 Normalized directory separators for URL mapping
Merge branch 'master' into iss2900
Fixed #2900 Added agreement option to defaults and cleaned up code to standards
Fix for #2900

The original if statement would add the scrollable area incorrectly.
Fixed #2900 Added agreement option to defaults and cleaned up code to standards
Fixed #2894 Corrected entity conversion for plain text customer registration emails
Fixed #2888 Calculate total items sold (quantity) through sub-query

The table join for purchased line items caused cartesian product of order rows and purchased line item rows. For every line-item result, the order result columns would be duplicated and then factored into the aggregation functions of the query.
Merge branch '1.3.x'