[Hotfix] Threading and Logging

[MJC598]

What does this PR do?

This PR addresses a lot of things, mostly dealing with either some part of threading or logging.

1. Threads can now be specified to either run models concurrently or put threads towards Eigen
2. The move assignment operators now actually move items rather than copy them. This was propagated down through the entire project.
3. CMake properties were changed to GNUInstallDirs
4. Logging was given mutexes so that we can share sinks without race conditions
5. Discounting is now multiplying the discount to remove rather than subtracting the discounting rate from the value
6. Timestep inserts was updated to correctly insert in order
7. Documentation was updated throughout
8. Tons of new tests

What Wrike task is this associated with?

Don't you mean YouTrack? :)

Checklist before merging

• If adding a core feature, I've added related tests.
• This is part of a product update, and I've added an explanation of what is different to the changelog.

[MJC598]

Testing if we can link SOF-72 from YouTrack.

[ddbaptiste]

Just a few questions and a handful of requested changes. This is a lot to get my head around, but I like the idea of the functionality you're adding.