Drag and Drop

Used library https://github.com/RubaXa/Sortable to add drag/drop functionality:
-        Elements in list can be reordered by dragging and dropping
-        New element no longer automatically appends list. Instead, buttons change list element beneath control panel, which can be dragged (cloned) into list.
-        Above caused several bugs, but for now they have been [crudely] circumvented. Changing the new element and cloning it into the list looks much cleaner than creating a new element each time and moving it across, and feels much more interactive than simply appending on button click.
-        Array is now generated on click of button Run. Uses hidden divs within each list element for simplicity (rather than using a function to interpret commands from their list format). For now, window.alert displays contents of array, without the Arduino itself to test on.
-        Next requirement is to add an option to remove elements from the list. This should complete the fundamentals of the drag/drop part of the interface.

Minor bugfixes:
-        Gap in tabs removed
-        Control panel now fixed
(These should be checked on tablet since there may have been a reason they weren't already fixed)