Make sure plugins are always loaded in the same order.

Sort fist by load order, then by name. Sort the same
Between different installations, and not depending
on insert order, or whether the rows are created in different
order when syncing, updating and so on.

These issue may become hard to debug, and appear
out of nowhere.

git-svn-id: http://textpattern.googlecode.com/svn/development/4.x@5589 2fea6a4d-a838-0410-917b-93a53c48e9d2