Update layout.py

Make it possible to add a `context` parameter to the panel directive, which makes that the panel will use another context. Ie Panel('format', context=context.date) which will lookup the format panel for dates.
Accept panels with no name (ie: name is '')
add tests and documentation for using an optional context (to override the context of the view in which the panel is called) as argument in calling a panel
Merge https://github.com/mrijken/pyramid_layout into contextual-panels
Don't need a production.ini in demo.
Don't need.
Just a little documentation.
Correct documentation.
Add new contextual panels to demo.
remove redundant comparison
Python 3.2
Merge branch 'contextual-panels' of github.com:Pylons/pyramid_layout into contextual-panels
Explicate contextual panels.
Merge pull request #19 from Pylons/contextual-panels

Contextual panels