issue #312 - added getTitle() and setTitle(titleText) functions for grid group interface

Added getTitle() and setTitle(titleText) functions for grid group interface, when the group initially has or has no title. 

I have tested it with both ripple and the device, it works well.

I have added the code to the bbui.js under samples directory. If you want to merge it, I will add the code to src directory as well.