[Trinidad] nextAction/previousAction on singleStepButtonBar aren't supported

[Renzo Tomaselli]

Hi, I just hit this issue and then found that there is a recent jira 
open for it.
Since this component is totally unusable without action/event bindings - 
I just need to know whether this issue can be fixed just by removing 
PropertyKey.CAP_NOT_BOUND from props listed in UIXSingleStep.java or 
there is something deeper to solve.
Just to be sure before turning on something else.

Thanks -- Renzo