When creating a quick note with `nnn` on the command line, instead of
creating an 'untitled note' if no title is passed, we create a note that
is named after its creation date.
Instead of finding the notebook at the wikiroot, we directly change the
current working dir to the notebook for the runtime of the zk command.
This has a couple advantages: Any other commands executed will also pick
up the correct directory, and creating notes in a specific directory
also just _works_ by giving a directory in the notes dir even if we are
somewhere else.
We use a custom zk indirection which ensures that any short alias for
interacting with the zk wiki will actually act on the globally assigned
wiki (by ensuring notebooks dir is "$WIKIROOT").
Local wiki requires the '$WIKIROOT' env var to be set, pointing to the
root of the (zk) wiki. So we only create associated aliases if the wiki
actually exists on a machine.
The note dir is in fact our `$WIKIROOT` so we set it to that by default.
Also took the chance and added a small 'cd' command into the note dir,
using `ncd`