Each Table should have a default CSS for all rows and all cells.

[mercere99]

Right now each cell in a table has its own Style object, as does each row (plus one for the table as a whole). We should be able to specify a default cell style or row style without needing to go through and change every single cell/row manually.

The difference between these approaches will be especially notable when tables change size so that new rows or cells are created. If a default style is present, they can be made to look correct without much additional work.