[development] Core scripts cleanup

[Khalid B]

I also like the check within cli to see if it was being invoked from
the web.

The discussion of the cli script being under DocumentRoot or not
has to be brought into context of previous discussions on what
should be under there and what should not.

At one point we proposed that Drupal should be split between
files under DocumentRoot, and files that are not under that.
The former would be all .css, .js, index.php, theme stuff, ...etc.
and the later would be all includes, and (arguably) .module
files.

This was in the mailing list, someone can dig it up.