[twill] Hacked some new commands

[Titus Brown]

-> > <snip a list of useful commands>
-> 
-> One could think of distributing a library of extension and keep the core twill
-> nice and small.

Hi, Michele,

it's already pretty large & bloated ;).  'commands.py' is quite long...
The question is whether or not we can keep it from getting worse!

I was thinking about putting in a 'twill.extensions' package that would
be available via extend_with, e.g. rather than

	extend_with twill.extensions.foo
	
you could just do

	extend_with foo

(This solves problems with paths that would crop up if extension modules
were distributed with twill currently.)
	
This package could contain modules with useful but less-than-mainstream
functionality (whatever *that* means ;).  One immediate candidate for
removal is 'formaction', which should not be needed by many people but
is critical in a few cases.

--titus