Add constant to control deprecated js loading
* constant is off by default

*Also...*
* Wrapped WPeC version constants in if blocks.  This will let developers put something into their wp-config.php file that bumps version numbers automatically to force script reloads, or perhaps for other reasons  My preferred insert is appending the time stamp of the wp-e-commerce.js file to the version stamp.
Merge pull request #1170 from JeffPyeBrook/pr-issue-1125-deprecated-js-load

Add constant to control deprecated js loading