1.3.7 Release
Merge branch 'issue/3116' into 1.3.x
1.3.7 Release
Added ShoppServices must-use-plugin (mu-plugin)

This plugin replaces the need for wp-load.php scanning though we lose the performance gains of using SHORTINIT. At the same time, the purpose of the plugin is to load early enough to block loading other plugins that may bog down service requests while still loading the core of Shopp necessary to support the service. This makes service requests for our various resource server scripts (images, scripts, styles) as efficient and reliable as possible.

Props to WP Migrate Pro for developing the technique and clifgriffin for the recommendation.
Change the script server request to always use a fake Shopp endpoint
Remove standalone stub support from image and script services
Removed the wp-load scanning
Added system preferences to install/uninstall the services helper plugin
Fixed #2860 Stop using globals to derive plugin path constants
Removed standalone services request condition

No longer necessary with the mu-plugin approach
Protect the data integrity of the ShoppTax::rates() call
Merge branch 'issue/2860'
Merge branch 'todo/tax-rates-cleanup'
Merge branch 'feature/3122'
Version change to 1.4dev