#318 Hover detailed tooltip on canvas

[High Performance Coder]

For most items, it might be useful to display a detailed tooltip (if that information is present) is a scrollable text window. For Ravels, it would be useful to be able to see tags that might be too large and get cropped by the Ravel renderer. For sheets, it could be useful to display cell contents that are too large.

My idea is to do the detailed tooltip in JS as a timer, so hover over a location for more than 3 or 5 seconds, the popup the tooltip. Need to destroy the popup again on mousemove over the canvas, perhaps.