Initial support for truncation in TextBox and TextGraphic.
Their base class, TextGraphicElement, now has a truncation:int property. It defaults to 0, meaning "no truncation". Setting it to a positive integer such as 3 means "truncate to 3 lines", or fewer if 3 won't fit. Setting it to -1 means "truncate to as many lines as will fit".
Truncation does not work when lineBreak is "explicit".
The truncation indicator is a locale-dependent resource, the same one as for Halo text: the "truncationIndicator" resource in the "core" bundle. For en_US it is three periods; I don't remember why we haven't been using a single ellipsis character.
TextGraphic implements this property using the new TruncationOptions class usable with TLF's TextLineFactory. TextBox does not yet implement truncation, but will.
There is currently a TLF bug that if you apply truncation the Flex styles are ignored.
QE Notes: Please test changing the truncation property at runtime, and switching to a locale with a different truncation indicator.
Doc Notes: None