Refactor using Generics and removing use of rawtypes

[GCHQDeveloper314]

Describe the new feature you'd like Full use of Generics throughout the Gaffer codebase and removal of all (or all possible) code which uses rawtypes. This will require refactoring of various parts of the codebase. For example, there are places where a raw collection is used to store distinct types of parameterised Objects in a way which is incompatible with Generics (because this is unsafe).

Why do you want this feature? Currently there are various instances of casts being made which could be removed if Generics were used fully/correctly. Removing these casts would improve readability and make better use of the benefits provided by generics. It would also remove various compilation warnings and IDE warnings.

Additional context This PR comment describes a typical example of Generics problems. See also #3048.