Comment 8 for bug 1747653

I went with convert-to-upper-case.

The first-character-checking was a bit more involved because of a bug in wxWidgets -- but since it affects all wxGrids with textCtrl validators I developed a workaround for it too.

The main grid editors in 5.0 don't use validators, so I'll leave the workaround in 6.0 along with the rest of this.