[development] Pathauto scaleability - path column in node / user table

[Khalid B]

> This is a faily simple, albeit fairly large patch. Do we have any
> volunteers / naysayers?

This will be a big performance boost, and chx will not complain
about the number of queries to url_alias when devel.module is enabled.

>From Moshe's comment, do I understand that we will keep the
multiple alias (i.e. one url can have multiple aliases), but only
optimizing it where nodes are concerned?

Say "node/123" has an alias of "this_is_an_article". Are we going
to have that alias in the url_alias table AS WELL AS in the node
table? If so, this can lead to data integrity issues, where the alias
in the node table says one thing and the ones in the url_alias says
another.

If we forbid node/123 aliases from going into the url_alias table, then
it is not an issue.