Prepare the Note and NoteStore classes for reading in data

Added Javadoc to Note's constructor. Added a new constructor to
NoteStore to allow it to be filled from an existing NoteStore.

Signed-off-by: Jamie Redding <jamieredding2694@gmail.com>
The xml reader is completed but not yet implemented

Reader has been finished and a test class has been made to test the
reader. The reader reads in data from storage.xml, checks the structure
is valid and then creates a NoteStore from the data.

Signed-off-by: Jamie Redding <jamieredding2694@gmail.com>