Some changes in CSS of Firefox OS demo
Compact Firefox OS demo into one file

The Firefox OS demo is store into only one HTML file now and use
some Javascript lines to change the content.
Fix align of undo button

When the equation's height is small than button's height the buttons
will not be aligned. We change the CSS to fix this but now one
button can cover part of another.
Update demos

For Firefox OS some changes was made and now the demos was updated.
Update documentation

* Remove information about double click in documentation.
* Remove information about double click in source comments.