Update FacebookImpl.java

two new methods in Facebook interface to get profile picture for diffenrent sizes (bigger than 200x200 that is Picture.large

Returns the url of the current user's profile picture (usefull for 480x480 and 600x600 sizes).
 
URL getPictureURL(int width, int height) throws FacebookException;
URL getPictureURL(String userId, int width, int height) throws FacebookException;