Expansion rework - resolve nested iteration issues.

Rework MapIteratorsFromScalar to:

* recursively expand any nested variable references so that all lists that
may be encountered during final expansion can be mapped to the iteration
context
* map any remotely referenced scalars to local scope primarily so that a
complex variable can reference a mapped list and a scalar
* rewrite "." -> "#" in place to more carefully ensure the proper "." is
modified (could be a bit better still)
* avoid mapping explicit this.* variables (may need more thought)

* add some tests and pull a few that now pass from staging
Add gentoo UID differences to acceptance tests
Clean up output of xml_diff in acceptance tests
Allow use of special this.* variables in handles

Move the handle expansion after the other variables are introduced.
RM #1554
Merge remote-tracking branch 'baptr/expansion'