uix:ColorPicker space effecient interface and add missing Documentation

a) A  new space effecient interface
    - RGB, HSV TextBoxes and Sliders,
    - Alpha and HEX: text boxes
    - More space for the Color Wheel

b) Add missing Documentation

This is the new Look::
![snapshot3](https://f.cloud.github.com/assets/788023/450284/ceb6c2c6-b28c-11e2-8dac-c6bfc9fe9280.png)

Note:  To checkout this change run the following commands::

    cd $KIVYDIR
    git pull
    git checkout color_picker
    python kivy/uix/colorpicker.py