Paint-28 - add custom icons for rest of Shape cursors

[greenfeld]

Dev.laptop.org issue #4315 (and maybe an unknown b.sl.o issue?) added a few more custom icon cursors for Shape tools in Paint build 28 (available from activities.sugarlabs.org).

However the Line, Free Form, and Polygon shape tools were not given custom cursors with this build. The last one is somewhat confusing since the Star tool was given a custom cursor, and the the number of points can be changed on that too.

These three items should be considered for custom icon cursors as well so all Shape-menu selectable shapes have custom icon cursors in addition to their Radio Button appearance up top.

[quozl]

 http://lists.sugarlabs.org/archive/sugar-devel/2010-October/027738.html is a patch using icon cursors by Ayush Goyal.

[godiard]

Reviewed by James Cameron.

Commited in git.