Also add separate file to handle drop-logic.

#671

#664

Stretch across the whole line.

The default value overwrites the value set in the parent constructor 
(Javascript...). Therefore the value needs to be intialized explicitly 
after the parent constructor has run.

#657

Mouuseenter, mouseleave for list and items are now always active and no 
longer added after the drag has started (they check of a drag operation 
is going on though). This makes the code simpler and more managable.

#634

#632

#631

#626

This fixes an issue where items could be added to only-one-item lists 
with replacement, when the  item to be replaced has the same list as 
origin.

#624

Fixed by using styles as in text field to define the background color

#625

#611

#611

#613

#611

#552

#621

#613

#618

- Prevent input of 'Dead' keys

- Remove unused imports

#599

Before it was just the bottom helper row.