Vishnu: Added the ability to add a section to a board.

Recently during a retro, we had a need to add a new section to the existing board with 50+ stickies. We could not do it and everyone felt this was a very basic feature missing. And that it needs to be there. Because of this, we had to create a physical wall with all the sections and add the new sections on sheet.

After some thought, I felt at least add a section feature should be there. We can think about delete/edit existing sections. But definitely add a section should be there.

So here it is :) try it out first...I've given it a shot on my local. It works fine. Have kept it decent and simple.