Can be useful when RWebWindow data damped to the files

One requires appropriate search method to found primitive and pad to
which it belong

When JS-side renders such objects, NDC position is calculated.
Now this position applied back to the server to preserve it.

Object will be referenced from client and updated correspondently

Used for different settings provided by JSROOT, try to avoid full
objects streaming like TFrame or TPaveText 

Also for web-based canvas we need such objects to preserve different
attributes, which can be changed by client 

Currently these are "&key=XYZ" for WebWindow and "&batch_mode" for all
kind of web widgets

Any extra URL options, configured for that window, will be inserted
before that window

Qt Scheme Handler provides info to the client that qt5 runs on the
server side and therefore connetion properties should be adjusted.

This could be used to insert specialized information, which is related
to WS handler or display engine like CEF/Qt5

Its content was moved to cefdisplay and qt5webdisplay

It is default way how CEF configured

One should be able to run ROOT without setting extra path variables

Qt5 now requires that custom "rootscheme:" registered before Qt
application created. Therefore now there is no separated handlers for
different window - single handler created once. Works now with only
THttpServer instance (like in CEF), can be enhanced later for many of
them.

Special handling of file responses required.
When file not exists, 404 reqply shoould be returned

Also try how RWebWindow runs with the http protocol

With WebGui.ForceHttp: 1 rootrc parameter all web window will use real
http server for communication. It can be important for some JavaScript
libraries which does not support redirection with specialized protocol
names.

With the time they tend to modify some methods.
To coupe with such changes, we will try to use #ifdef - as long as it
works.

Simplify makefiles. In principal, one could use builtins for openui5
sources.