Provide more getter helpers for templates; use fewer extraneous objects

[srawlins]

I think it is a smell in a template to reach out of a ModelElement into strange places like .packageGraph. The desire to access information on the packageGraph field is not bad, but it should be more accessible so that templates don't have to jump through a UML diagram to get at what they need.

In the standard templates, there are actually only 28 instances of using nested properties at all:

git grep '{{\s*[a-zA-Z_]\+\.' lib/templates/ |wc -l

Many of these are perfectly innocent. I don't see a reason to change {{self.name}} or {{parent.kind}}. As a matter of fact, when filtering out {{parent and {{self, the only other case is using {{packageGraph.