fix #761 test.aria.widgets.icon.IconTest failing on IE10

This commit fixes test.aria.widgets.icon.IconTest which started
failing in d483056c6edf8064781d069101fdca40b874ac15 because the
type of absolutePosition.top in the popup configuration changed
from json:Float to json:Integer (when the config bean was moved
from aria.utils.DomBeans to aria.popups.Beans).

This commit restores json:Float in
aria.popups.Beans.AbsolutePositionConfig.