FLUID-4525 UIOptions Jumpingness

[Antranig Basman]

I've pushed a few fixes to my branch at https://github.com/amb26/infusion/tree/FLUID-4525 which as far as I 
can see resolve the two issues we saw on Johnny's FSSFive site, although their status is still rather 
dubious. Like cindyli, I also couldn't uncover the real cause behind the behaviour of the enclosing div for 
the sliding panel in some integrations to be of zero height, but in others to attain exactly one lineheight, 
leading to a gap appearing above the sliding panel button on first render - but I have added behaviour to 
FatPanel to make it go away by explicitly setting the div height to 0 as soon as is feasible.

The jumping issue I have tackled by changing the order of various operations with sliding panel - eschewing 
the use of jQuery "slideUp" and "slideDown" in particular since these seek to alter the visibility of the 
animating element at the end of the animation - which I think causes a greater risk of jumping as the 
browser has to reassess the visibility of the entire iframe tree. The new strategy relies 100% on height 
manipulations of the iframe and its parent div in the document - as well as rescheduling the "show" 
operation to make sure that animation doesn't start until rendering of the iframe contents has completely 
finished (in fact, there is no explicit "show" operation at all any more, we simply defer to the existing 
"DOM height changed" pathway).

Please test these out and see if the problems indeed seem to have gone away.

Cheers,
Antranig