wbo is now more observable

(and add type annotations)

* Add mover skeleton

Atm it is just the eraser with new icons and renamed variables

* The mover not detect the object to move

* We can move ellipses and rectangles

* The mover now moves all types of objects

* Add the move everything functionality

* Aesthetic changes

* Replace the use of const and let with classic var

* Undo few commits

* Start the transform-translate implementation

* Mover now moves with transform translate

* Put the function to get the translation matrix in the Tools

* Shapes (ellipse, line, pencil, rect, and text) now properly load translate coords

* Add the transform-translate to the createSVG functions

* Done movement using transform-translate

* Fix parenthesization bug in the SVG create

* Fix comment about mover states

* Undo translation loading from Ellipse, Mover, Pencil, and Text tools

* Makes the board send update message to the mover as needed

* Remove the old code from the line tool too

* Simplify the mover tool

See #86

* update the mover icon

* Merge the mover and the hand tools

* Improve preview for pre-rendered elements

* v1.6.0

Co-authored-by: Paolo Bolzoni <paolo.bolzoni1@studenti.unipr.it>

Node 8 is still the default on ubuntu 18.04.
See: 63db84f7dd

There are now several different configuration
variables through which WBO can be configured.

Thanks @iblech

Fixes #34

This makes the code more readable.
Also add the automatic deletion of empty board files.

Fixes  #28

Closes #5

Unload boards from memory when that last connected user goes away.

Some work was done on the client-side too, and board loading should now be much faster.