Renamed files, changed how functions are defined

Renamed hexagon.js -> board.js
Renamed display.html -> index.html
Changed function statements to function expressions as they are apparentely the more correct way to do it in javascript
Removed window.onload function in hexagon.js because it is not required.
Moved where and how the script is loaded in the html file.
Changed the name of the project and description in the manifest.