feat(on_MTEvents): send width and height of object on MTEvents

When multitouch events happen (like touch, drag), we are also sending
width and height of object to the server
feat(util): add object with utilities methods

These methods are only available in the wams.js library, are not
available for user.
feat(util.offset): method returns offset of element on page

Method gets element and returns element's left and top offsets.
It is calculating by adding offsets of element and all its parents.
feat(util.isDraggable): returns if element can be dragged

SOLUTION IS TEMPORARY

This method returns if element can be dragged on the page. This method
is to prevent bug when multitouch elements lose focus and user start
dragging <html> or <body>.
Method checks presence of class 'ball', for bigger portability we should
check instead that this object is among MTObjects array.
feat(wams.on): send offset of element, not touch point

Previously with element position touchpoint was sent, and to find offset
of element, it was necessary to subtract touchX and touchY coordinates.
Currently, actual offset of the element is sent over network.
fix(wams.on): check if element is draggable

This check here to prevent bug, when focus was changing from multitouch
element to <html> or <body>.
fix(on): assign handler function to variable

Eliminate anonymity of handler function by assigning it to variable.
chore(on): fix indentation
feat(dispose): provide dispose function to delete all MTObjects

This function destroys all MTObjects and all event listeners
feat(sharedWorkspaceWithRacer): start new example

This is copy of sharedWorkspace example, but instead of wams and
socket.io, it is done using racer project. Racer allows to
automatically sync data between clients.
chore(package): add racer dependencies
chore(sharedWorkspaceWithRacer): stop livereload in browsers
feat(racer): provide basic functionality of data models

Add code on server and client for racer to work.
New client adds field into users and screens model, and deletes it
before unload of webpage.
Also change model and display on resize of the browser window.
fix(elements): provide default coords and dimensions

Provide x, y, w, h for all elements in model
feat(isEmpty): function checks if object has no own fields
feat(workspace): calculate workspace border on server

Move calculations for workspace size to the server.
fix(app model): do not subscribe to model in render function

We subscribe to model outside of render function, so this is
unnecessary.
feat(minimap): set minimap settings on server
feat(browser): show elements on page after load
feat(extractColor: function that gets color of element

This function get color if element is already on page, or if it is not
on page, it adds element and then deletes element.