[API REVIEW] RT-29194: Add property to specify how the PopupWindow's position is interpreted

[LUBOMIR NERAD]

Hi All,

this request comes from RT-28775. It should make it easier to set the 
PopupWindow position on screen by changing the reference point 
associated with the x, y coordinates. While for regular windows this 
point is in their upper left corner, for popup windows this point (by 
default) will be identical with their content origin. So if the content 
has some additional border (shadow), this feature will make the popup 
position independent on it.

You can find more information in:

https://javafx-jira.kenai.com/browse/RT-28775
https://javafx-jira.kenai.com/browse/RT-29194

To control this behavior there should be a new boolean property in 
PopupWindow. The proposed API is:

public final void setAlignWithContentOrigin(boolean value);
public final boolean isAlignWithContentOrigin(); (maybe "get" prefix is 
better here?)
public final BooleanProperty alignWithContentOriginProperty();

The default value will be set to true (the new interpretation of the 
popup window position).

Thanks,
Lubo