Added exist("elementId") and doesNotExist("elementId")
There was a problem with displayif when the forid does not exist.
Fixed adding style attribute to the element. Use javascript element.style.StyleAttribute = xxx. Note: for the display changed from "inline" to null. This way the style defaults to the tag/class not just to "inline"
modified evaluateCondition to use math.js evaluate method instead of my parser. This allows use of functions in math.js and can have more/less parameters than 2.
Fixes for ISSUE_338.