Put chart subclasses and Chart into separate files
Added framework for popout boxes for the axis picker
Added framework for drag and drop
Added skeleton creation of draggables from experiment variables and droppables with adjustable widths
Draggables snap to and snap back from droppables
Targets accepting different classes; added dummy box so animations don't effect selected axes variables
Added button labels for each axis shelf; removed axis name from droppable; need to make dropdown positions offset from left
Added button labels for each axis shelf; removed axis name from droppable; need to make dropdown positions offset from left