ID type reconcillation

[TheMrMilchmann]

In #199, support for type aliases was introduced. Aliases are important for declaring type-safe ID types and are used in the spec in several places for exactly this purpose. However, not all ID types have been extracted into aliases yet and there are still a couple of places, where the old "plain" types are used for IDs for which an alias exists.

To clean this up ahead of a stable release, it is necessary to go through the entire specification once again. For all ID types under com/gw2tb/apigen/internal/spec, an alias should be created in common. Further, those aliases should replace the previous primitive types in places, where the ID type should be referenced.