Substantial behind-the-scenes refactoring was also done as a part of this issue...
The model now has a single TestCentricProject, derived from TestPackage, rather than a TestPackage.
Properties TestFiles and PackageOverrides have been removed, simplifying the model substantially. The TestCentricProject class now takes care of these functions itself.
Some rudimentary events have been added to allow the presenters to respond when a TestCentric project is created, unloaded, etc.
This is part of Epic #3.
The purpose of this change is to facilitate testing of the work to be done in later steps.
Initially, some of the menu entries will lead to a NotImplementedException, but these will be removed as work proceeds.