Partial implementation of space-after functionality--mostly working, but

Partial implementation of space-after functionality--mostly working, but
some remaining problems:

1.) relying on a static variable to carry space-after value from previous
block to current.  (BlockLayoutManager is be instantiated for each block
instead of being in memory for all blocks--bad design?)

2.) The space-after of a block ending at the bottom of the page is not
currently being added to the beginning of the subsequent page.

git-svn-id: https://svn.apache.org/repos/asf/xmlgraphics/fop/trunk@197004 13f79535-47bb-0310-9956-ffa450edef68