I have created a skeleton UI for the Conditions builder. I have committed the additions and modifications. So, you all can have a look and tell me what's missing or wrong. One thing I would like to point out that i have not yet added context sensitive form elements that are created on selection of certain items in the UI. So, you will find only variable types listbox in variable creator but no form element to input the attributes for the variable and no list of available variables is created when you select operand type as variables in create conditions tab.
Also, All the div elements for creation, edition and grouping that are currently not controlled by the menu above will be controlled later.
So, You can consider those as not errors. Thus, its just a basic idea of the future UI.