Drop position when scrolled corrected

Using pageX instead of clientX, etc. ensures the drop ends up at the
right place. Fixes #49.

Also did some code cleanup.
Clicking on a resource runs it

And clicking elsewhere on a page without a top-level backside turns off
all widgets.
New version of a test file
JQuery UI now includes accordion

And menu is removed since not used.
Element attribute chooser uses accordion

Looks nicer and uses much less space.