Currently with screem helpers (version <= 1.1) you can only execute all
of the helpers in order on a page.

This isn't very clear, and also not very useful.  As such a better method is
as follows.

(the editor menu)

------------
| blah    >|
| blah    >|
|__________|
|          |-----------
| helpers >| All      |
|          | Helper 1 |
------------ Helper 2 |
           | Helper 3 |
           | Helper 4 |
           ------------

So a click on the All option would perform the same action that is currently
performed.  However to give more control you could also just select a single
helper that you wanted to execute.

Another possible option is to allow the definition of helper groups.  Then
each entry under the helper menu could be a submenu with a set of helpers that
belong to that group, again with the option to execute them all, or just one.
