remove sessions controls from /pixeleditor
make the load button a file input in /pixeleditor
update save menu for local saving in /pixeleditor
connect load input to importing models in /pixeleditor
allow PixelCanvas to be constructed with jQuery object
add utility to convert exported models to images
connect save menu controls to save actions in /pixeleditor
update dimensions field in settings menu when dimensions value updates
export visible dimensions from GridModelBuilder#exportModel