1.9.0 Bug fixes, convert to JSMO.ajax()

Convert from separate page as ajax endpoint to the (newer, now preferred) mechanism for module ajax calls, the JSMO.ajax() function and redcap_module_ajax() method. With thanks to @grezniczek.

Bug fixes for popup save button behaviour:

• "Save & Stay" then "Save & Exit" would have popup window redirect to Record Home instead of closing.
• "Save & Stay" not persisted in UIState