Added fix for scriptable if logic + stat_test

Added fix for multiple nested if/else statements by unwinding conditionals and inversions instead of clearing them.

Also added stat_test which tests a stat against a DC. A random number between 1 and the stat is selected, if it meets or beats the DC, it passes. This gives different odds than saves, and allows for a random chance that can be more fine-tuned than saves. If you don't like the implementation and want style to test stats (like a d20 roll + modifier) then I can change the implementation to that.