ControlSize management and CPRuleEditor/CPPredicateEditor alignments

Hi guys,

Cocoa enables developers to use different control sizes : `Regular`, `Small` and `Mini`.

This PR enables Cappuccino developers to set their controls size via xCode or programmatically. Every control now has a `setControlSize:(CPControlSize)aSize` and a `controlSize` method which are the equivalent of [`NSCell` methods](http://goo.gl/nSZV6g)

## ControlSize management

Control size management has been done for the following **Aristo** and **Aristo2** controls :
* CPTextField
* CPButton
* CPPopUpButton
* CPCheckBox
* CPStepper
* CPDatePicker

*Note:* A new test named `CPControlSize` has been added to `Tests/Manuals` directory. Here are a screenshot for both theme:

**Aristo**
![cappuccino-aristo_controlsize](https://cloud.githubusercontent.com/assets/1447243/3885373/d0298d6a-21c0-11e4-948e-3474fd149471.png)

**Aristo2**

![cappuccino-aristo2_controlsize](https://cloud.githubusercontent.com/assets/1447243/3885375/d02ad15c-21c0-11e4-9e62-6ba15fc2b74b.png)

No new images is needed: `CPView` `setBackground` method uses CSS3 property `background-size` to set the correct background image size. 

## CPPredicateEditor/ CPRuleEditor alignments

As we now are able to set the control size, this PR also includes `CPRuleEditor` alignment corrections (issue [#2162](https://github.com/cappuccino/cappuccino/issues/2162) using `CPSmallControlSize` of each controls. The existing test in `Tests/Manual/CPPredicateEditorCibTest` has been updated to show the following right expressions : 
* Boolean
* CPDatePicker.
* CPPopUpButton

![cappuccino-cppredicateeditor](https://cloud.githubusercontent.com/assets/1447243/3885374/d029fa20-21c0-11e4-8f97-ed4377a65d5e.png)

This condition has been added to avoid sending a nil action to a nil target. This case happens when the CPDatePicker is initialized within a CPPredicateEditor.