Support zero-byte delimited input/output placeholders for `run`

[Michael Hanke]

ATM the related placeholder are primarily geared towards command-line based parameter passing (e.g. the get shell-quoted). This makes it unnecessarily difficult to further process them.

I propose to add another set of placeholder that are zero-byte delimited, and not otherwise modified by quoting.

[Yaroslav Halchenko]

Should it may be just be the config setting?

[Michael Hanke]

That is a possible setup that would avoid placeholder proliferation.

So they default would be something like shell-quoted-space-separated-list (which is what it does not), and there could be any number of future alternative modes.

This would imply that the run-record itself would need to also capture this information, otherwise reruns would not work.