Improve all inline tooltip documentation (doc comments), include exceptions info and all parameter info

[abelbraaksma]

As in the title. Esp. now that we've added all the proper null-checks in #127, we should clarify for each function what input would cause ArgumentNullException to be thrown. Tedious work, but it must be done ;). Keeping it up-to-date afterwards should be easier.

[abelbraaksma]

Finally, this is done. All exception information is now in the tooltips, and the limited ability that F# gives us for some syntax coloring in the tooltips is used for better recognizability.

Example:

[abelbraaksma]

The comments were actually from #183, which accidentally included these document updates as well.

@bartelink Since this causes quite a bit of potential merge issues, esp if I go for static member next, I am going to move these in. However, ping me here if you still want to re-review this. Keep in mind that I've been seeking parity with seq in F# where applicable. A lot of wording is borrowed from there.

[bartelink]

Please don't wait for me at any time - am fine with doing chaser reviews
Good point re aligning with Seq - if not already prominently mentioned, goot to have that high p the README.md
Though not having where is fine with me!