Revised SQL in viewall.php to display all notes which is created and
shared to current user as well as category information
Adjust the layout of the list of study notes
Added notification message when current do not have any study notes
Removed unused code
Allow user to 'uncategorize' a notes
Display category name together with notes information in viewall.php
Adjusted table column width in category.php
remove 'manage note' button
1. Added simplified chinese language
2. removed unused language string
Tune SQL in viewall.php
Fixed delete bug for note category and relation
Hide categories selection box when user does not have any notes