Cellnav skipping every second col, header not scrolling when body scrolls

[PaulL1]

Cellnav is skipping every second column when using the left/right arrow. I think perhaps this is related to the change I did in #1606, as I pushed the rowHeader in the front of the cols array, and for some reason it is created with index == 1. I'll look at renumbering all column indexes when the rowHeader is inserted.

Also, when scrolling using cellNav, the header doesn't appear to scroll, whilst the body rows do. Looking to see what may be causing this as well, perhaps related to #1591.