Improve test coverage of the service classes

[joepal1976]

Pretty much all of the core logic is implemented through service classes with static utility methods. These are all written to be agnostic as to what the user is doing with the interface. Ideally, they should have close to full direct test coverage.

At the moment, only a few of the service classes have direct test coverage (ie unit tests that calls the method of the class directly). However, as the classes call each other, a few classes have indirect test coverage that way.

At least the following very important service classes should have direct and specific unit tests:

• AssetService
• ClothesService
• LogService
• RigService
• SystemService
• UiService

The other service classes (such AnimationService, the config sets etc) are less critical.

[joepal1976]

Good enough for now.