'print' helper function

[JohnMertz]

As discovered with recent vulnerability fixes in the current release, it can be clumsy to simply 'print' everything to the WebUI in-line. This requires that variables are properly sanitized every time a new output line is added, which can be very easy to make mistakes with. The best solution is probably to replace every 'print' function with a 'clean_print' helper function and replace all applicable instances of 'print' to use that instead. Then, we will be guaranteed that new output using that helper function should not be vulnerable.

This is a lot of work and is best not to get in the way of creating stable-ish the Beta images.