Added "EndsWith" and "StartsWith" public static final methods in QString.

Added "EndsWith" and "StartsWith" public static final methods in QString class. Also whatever pieces of documentation was lacking have been fixed.
They are working perfectly. I have tested them. See the code here: 

https://gist.github.com/vaibhav-kaushal/c85219773e7a13fb2e1b

It is a single file which can be used to test the logic. You can download and run it. It gives me this: 

![screenshot 2014-12-19 05 42 33](https://cloud.githubusercontent.com/assets/2824682/5498220/e7152174-8741-11e4-8bd6-2704020395df.png)

Will write unit tests shortly.