fixed #tree bug (could not open previously created trees), added more DB functions (closing, compaction)
minor code relocation, beautifying
DB#count renamed to DB#trees

Signed-off-by: Christian MICHON <christian.michon@gmail.com>
updated documentation

Signed-off-by: Christian MICHON <christian.michon@gmail.com>
release 1.0.0

Signed-off-by: Christian MICHON <christian.michon@gmail.com>