House Keeping: Add function uiElementDisplaySet or uiElementSetDisplay

[ElSkunkito]

I used function pointers to uiShow/HideElement
instead of creating a uiXX function

The new fucntion should the css style.display
if parameter is true to "inline-block",
and if false to display="none"

See source for 3 instances of
var f_pointer = uiHideElement;