Update the tree conflict detection design note with more info on tree conflicts involving directories.
Update the tree conflict detection design note with more info
on tree conflicts involving directories.

* notes/tree-conflicts/detection.txt
  Clarify use cases 1, 2, 4, and 5, which involve "deep" tree 
  conflicts.  Illustrate with an example of a deep tree conflict.

jmckaskill/subversion,jmckaskill/subversion,jmckaskill/subversion,jmckaskill/subversion,jmckaskill/subversion,jmckaskill/subversion,jmckaskill/subversion,jmckaskill/subversion