Fixed majority of tests

Majority of tests working now.  The bulk of the problem was in the
RepeatLastCommand function.  It commonly opened nested undo and linked
undo transactions.

Still have to resolve one case.  What happens when you intentionally
create an empty linked transaction as is the case with a counted insert?
If the user types the sequence `3i<Esc>` then we have an empty linked
transaction.  Need to resolve this
Fixed remaining tests

This should put us in place where #1387 is fixed.  This is a moderate
change to the undo code so I want to bake it for a week to make sure
nothing bad is looming here
Removed appveyor restriction