Fix #1685: Remove col.index from most code

Removed col.index everywhere it appears, except for in the cell content
templates, which appear to use col.index in creating the cell class.

Added a column renumber to buildColumns to always give every column an
index starting at zero.

Reviewed every tutorial to see if there was breakage.  Found breakage, but only one item that related to this change (the rest was pre-existing).

One outstanding defect that I couldn't resolve (nor see how this change caused it, although it clearly did) is that tutorial 113 - adding and removing columns - doesn't correctly splice a new column in the middle.  The data turns up, but the header widths appear to be slightly off, and therefore everything is wrapping.  Upon scrolling the data fixes itself, the headers don't.

Looking for a review and suggestions on what could be causing that, rather than expecting this to be merged.