A border is a visual decoration around a report field. Each of its four
edges (top, left, bottom, and right) is a
BorderEdge and may be
null.
author: Jim Menard, jimm@io.com
Writes this border as an XML tag. Asks each edge to write itself as well.
If
Border.isEmpty returns true, returns without writing
anything.
Parameters: out - a writer that knows how to write XML