This patch adds two options for controlling positioning of icons on the
<li> "Keep icons within screen limits" controls whether pinboard icons
are allowed to go partially off-screen to the right and to the
bottom. Disabling this option makes it possible, for example, to put
an icon on the right-most border of the screen, even if it has a
<li> "Icon grid step" controls the size of the grid on which icons on the
pinboard are placed. It has three settings: Fine (2 pixels), Medium
(16 pixels) and Coarse (32 pixels and the default).