Added create/delete buttons.
Added a horizontal-panel to hold the buttons
Use a border-panel to layout main-frame contents

The border-panel lays out the panel containing the buttons on top
(:north) while the horizontal split lies in the :center.
Define Var "borders" to refer to the border-panel

By defining a reference to the border-panel, it's a lot easier to modify
in the REPL in order to tweak the layout of the UI.
Call pack!/show! as the final GUI setup step

Calling pack! last will allow the GUI to be sized to the content that
has been loaded, rather than possibly sizing the GUI to a very small box
if no content has been loaded yet.
Define delete-note to delete notes from the db

Notes are deleted based on their primary key (id).