BaseRouter (and Backbone.Router) lacked some of the capabilities

available to models and views. It wasn't possible to provide typed

custom options, for example. Our typing also didn't allow for routes to

be dynamically-constructed.
This change introduces new generics when subclassing BaseRouter or

Backbone.Router, allowing an interface to be provided for custom

options. This mixes into an interface (now provided in our version of

the Backbone typings) of standard options for the class.
The standard options have been updated to not require routes to be

specified.
The combined results are passed to preinitialize, initialize, and

constructor. This follows the same patterns used in Model and

View.
The routes static attribute can now be a function, which returns the

routes for an instance. This is run with the instance being passed as

this.
A new RoutesHash type has been exported. This maps to

Backbone.RoutesHash, and is easier to reference without importing

Backbone.
Unit tests have been addd to test all static attributes/fucntion

behavior. Since our testing uses TypeScript, the type-related issues

were also caught by tests.

Unit tests pass.