Primary motivation is documentation, but it will also hopefully simplify the code.
Also,
* Lower case the default output format names; this is in line with the custom ones (map keys) and how
it's treated all the places. This avoids doing `stringds.EqualFold` everywhere.
Closes#10896Closes#10620
This means that the current `.Site` and ´.Hugo` is available as a globals, so you can do `site.IsServer`, `hugo.Version` etc.
Fixes#5470Fixes#5467Fixes#5503