Convert all models to object type literals

[alancleary]

Currently many model types in the GCV are defined as classes. While this is useful when types are required to have methods as attributes this is mostly not the case. Any additional class related benefits are lost due to GCV's use of prototype-based mixins to add attributes to existing objects without mutation or duplication.

The main motivation for this change is to enable support for NgRx Store state serialization. Object type literals are serializable, whereas classes are not. By switching to object type literals, the store will be serializable, thus enabling additional functionality, such as support for GoldenLayout's popout windows which requires passing a copy of the application state to the poped out window.