Drag and drop images and support for math using mathjax

[andrea78]

Hi Robert, First of all thank you very much for building this amazing project. A star from me. It's the best whiteboard for teaching math I have ever seen.. it would be really awesome if it was possible to Drag and drop images from PC. It would be great if it was possible to add a mathematics tool which accepts LaTeX code in a text box, formats it using mathjax, and displays it on the page. There is a bug in the text tool. When typing text and deleting it with the backspace key, when I refresh the page, the text does not disappear. It looks like the text I have deleted earlier was not deleted.