Include what you use for library and tests

[syclik]

Summary:

We need to review all of the code and remove all the overincludes.

For tests, it's not clear to me that we want to have minimal includes. The advantage of having the broad library include is that it checks interactions; the advantage of including what you use is that it shows you what needs to be included and will be a whole lot faster.

I missed some tests when I fixed #236.

Description:

Some of the tests and most of the header files include more headers than just the one it needs.

Current Version:

v2.9.0