Improved caching.  May contain debugging info.
Improved toString methods and shortened XyDimension to XyDim.
Fixed center-alignment for header/footer.  Still lots of debugging stmts.
Fixed alignment issue and removed all debugging statements.
Cleanup in preparation for moving to DocumentBuilder land.
Previous commit made TableBuilder renderable.  Now committing before turning PdfLayoutMgr into DocumentBuilder and PdfLayoutMgr.PageBuffer into LogicalPageBuilder.
started at reverse end an integrated the proposed Document and LogicalPage into PdfLayoutMgr and PageBuffer respectively.  Nothing broken, but no real gain yet either.
Shuffled more pieces around to better separate PageManager from PdfLayoutMgr.
More preparation for moving PageBuffer to a separate class.
PdfLayoutMgr still presents a pretty rough interface to the world, but LogicalPage is the new class to use and PdfLayoutMgr can be cleaned up later.
Made all the table builder stuff work and align cell contents 9 ways
Fixed offsets within cell items so that each line of text is horizontally aligned appropriately within the text block in a cell.
Reduced some visibility and shortened some names.
Cleaned up test to make resulting PDF prettier.