Patch for the implementation of the improved float-placement algorithm

Patch for the implementation of the improved float-placement algorithm

Changes:
- merge in changes up to revision 432403 of the trunk
- extract LineBreakingAlgorithm and LineBreakPosition from LineLayoutManager and
  put them in the breaking subpackage (was in preparation for the side-floats
  implementation)

New features:
- minimum accepted fill ratio for pages: underfull pages which have at least
  this fill ratio are considered to be feasible breaks
- float-only pages; this may be parameterized
- big floats may now be split on several pages
- shrink- and stretchability of out-of-line object are now taken into account

git-svn-id: https://svn.apache.org/repos/asf/xmlgraphics/fop/branches/Temp_Floats@474218 13f79535-47bb-0310-9956-ffa450edef68