Several intropage updates
Several intropage updates

* Properly refresh page to prevent browswer hangs due to too many refreshes
* Use print over echo
* A few missing i18n strings
* Use prepared statements for database operations
* Move click functions into ready statement
* Formatting of space vs. tab
* Check for file exists before attempting to load theme css
* Remove some legacy debug code
* Clean up some SQL formatting
* Some conversion of double quotes to single quotes

xmacan/plugin_intropage,xmacan/plugin_intropage