Add javadoc to Val, StateMachine, and List-, Tuples-, and FingerTree-related classes and methods

[JordanMartinez]

WIP

I figured I should document this first to better understand how it works since this is still the part of ReactFX I don't fully understand.
Once I do, I'll better understand how Flowless works and thus how to solve some of its bugs.

[JordanMartinez]

K, looks like I just need to work on FingerTree now.

[JordanMartinez]

K, I think this is done.

[JordanMartinez]

I needed to update it due to getting a

ReactFX/reactfx/src/main/java/
    org/reactfx/util/SparseList.java:16: warning: no description for @param
 * @param <E>

Now it's done and ready for your feedback/review

[JordanMartinez]

Hmm... I think that about sums it up. FingerTree could still have more documentation, but I'm content for right now.