Add valuePostfix, maxPostfix, minPostfix, to postfix value, minimum and maximum

Added the following configs:

 - valuePostfix
Postfix a string to the display value in the middle f.x. "%".

 - minPostfix
Postfix a string to the display minimum 
f.x. "%".

 - maxPostfit
Postfix a string to the maximum f.x. "%".

Example image:
![auto-adjust-20140113-231333](https://f.cloud.github.com/assets/517111/1905555/271d8e58-7ca0-11e3-94cc-5fd5b5e76390.jpg)