Improved mobile Interface for webgcode

[dafzor]

Currently I'm using the webgcode web app on a phone and the interface could be slightly improved for it with possibly minimal work.

The enhancements I'd like you to consider are:

• button to clear the gcode (delete all text)
• button to download gcode as a text file
• making the previews show bellow the code editor in small screen size devices (or maybe a tab?) and allow the code editor to adapt to the width of the screen

These are not the only only improvements that can be made but possibly the easiest/fastest to do that would provide the greatest usability benefits.