Rename "fixed" template to "cloud"

[ericras]

The "Fixed" name is an anachronism from when the main template had a fixed pixel width. (There was also a "liquid" template which was abandoned that would now be considered responsive.)

Now that the main template is responsive it needs a new name.

We have basically one design now with an option to use "fixed" or "local" template. What distinguishes the "fixed" and "local" template is whether or not it fetches the CSS/JS from the cloud or from a local directory.