Remove application specific session variable

[toirl]

In commit 483d498 a new session variable was introduced. Unfortuantely this variable is only used in a ringo based application but not in ringo itself.

Even if this does not lead into immediate problems I consider this as a bad design and like to change this in a better approach:

Questions:

1. Why was this change needed? What was the actual error?
2. Can we fix the usage of the known "values" GET params?
3. Maybe we can use the values attribute of the view (which has been added in the meantime I think)