Merge JobInteraction Writers into one type

[jkeon]

Lots of duplicate types like DataStreamWriter, EntitySpawnWriter, CancelRequestWriter etc.

They all do the same thing and it's duplicated code to maintain.

Consolidate down to one.

From: #158 (comment)

While I originally wanted to keep the API separate and more clear about the context of what you were doing, Mike raised two good counter points:

• If we had to do unit tests for these, I'd only want one type.
• If a bunch of things like this took in a Dictionary I wouldn't be confused, and i wouldn't make a wrapper for Dictionary that changed the names of Add.