Namespace and Attribute textfields should not be prefilled

Please remove the default values from both the 'Namespace' and 'Attribute' fieldsets. I doubt if most people would use the values 'context_ui' and 'section' most of the time when building their contexts, and it makes the process of creating new contexts prone to error.

I think that having the examples beneath the fields as you do already is enough. Every time I create a new context I have to remember to change those default values... often, I forget, since they are already filled out for me, lulling me into a false sense of security.