Added some explanations to ScrollPane and Viewport to more clearly
document the usage of the "view" property to add the children.

This a merge of revision 1458918 from branches/2.0.x to trunk.


git-svn-id: https://svn.apache.org/repos/asf/pivot/trunk@1458921 13f79535-47bb-0310-9956-ffa450edef68