editor initial release
use Ctrl or Command key to edit
Disregard all TemplateElement nodes while counting element index
add gaps between elements;
save custom order in localStorage;
use px instead of relative units for element width and height;
temporarily fix priority issues by setting a unique priority to each element;
show highlight & editor when Ctrl is pressed while mouse cursor is over an element;
store elements of this.priorities array in the DOM order
store children DOM elements in this.items;
calculate Rectangle in packItems
Trim too big rectangles
don't set up a global variable
move gap property out of the priorities object; share gap between elements on the same level; save gap in local storage
Fix reprioritizing (https://github.com/Polyjuice/Launcher/issues/19),

remove cellWidth and cellHeight,
update examples to work with fixed px sizes.
Change default element display property to `block`
calculate available width/height excluding margins, borders and padding of the container
Make #resizeItem work back again for item index
Nested pj-sortable-tiles example, examples layout update
API fiddle helper added to examples
fix element selector overlay size. Width and height were not specified, resulting in 100% viewport size in Chrome and small size (200x200px?) in Firefox. The desired size of the overlay is the whole page (scrollWidth, scrollHeight)
avoid using ids that are not guaranteed to be unique within document
decouple pj-sortable-tiles-editor from pj-sortable-tiles (now pj-sortable-tiles-editor is placed outside of pj-sortable-tiles)
decouple pj-sortable-tiles-editor from pj-sortable-tiles (now pj-sortable-tiles-editor is placed outside of pj-sortable-tiles); control "editingMode" from the outside of pj-sortable-tiles through a UI control (such as checkbox) instead of CTRL button on the keyboard
change pj-editable-tiles-editor layout to be flexbox; remove close button
change sortableTilesId to sortableTilesSelector
hide values when there is no editedItem