Implement e-cell-height
Implement computation of heights from the e-cell-heights
Make sure we compute the height from that
Include spacing in columns and rows for the decoration lines
Add threshold to compute a "global" size 
Implement the two methods for row finding: by full thing, or by a factor.


Add editing
mouse grabbing for scrolling


1. Make sure that all values are updated on header changes and table
   model changes (they are slightly out of sync now)

* Correctness

	* Make sure we can boot and shutdown with no memory leaks.

	* Run Insure on the thing.

* Propagation

	* Row changes should be reflected in the subsets.