Added doxygen comments to tree.
Added comments to schoolmarm (Cygwin) configuration.

git-svn-id: svn://graphite/diminuto/trunk@575 5dfbf39a-1452-0410-8a97-9e58fedde8e3
Added doxygen comments to store.
Expanded tree and store unit tests.

git-svn-id: svn://graphite/diminuto/trunk@576 5dfbf39a-1452-0410-8a97-9e58fedde8e3