-Use sprm:CBrc attribute for all MS filter (for ooxml too).
-Extract general code to FormatCharBorder() method, it selects
the border side and decides whether add shadow to the border.
-RTF export has a color table, which must be filled with border
colors before the actual export.temp

Change-Id: Ic3ceae6e19ddc2ed5aaa8de85617f9a592289b4f