When palette does not explicitly provided in drawables,
create default RPalette and associated it with RFrame

Now it is plain class - no any complex attributes members

Let draw palette, perform zooming

Complete class renaming

Doing in two steps to keep git rename history clear

Each margin can be coded as string like "10px + 0.1"
Simple parsing is provided.

Potentially one can use RBoxAttr, but let not do it too complicated

Allows properly inject many messages at once

Used in eve for element selection

Add support of TGeoTessellated 
Reverse axes in TH2 col plots
Better support of TLatex topline/underline/crossline

Use JSROOT ProduceImage functionality.
Only if image name ends with "*shot.png", chrome --screenshot
functionality will be used

Using --dump-dom functionality of the chrome browser to store complete
HTML file and then extract only part of it

Try to use --print-to-pdf=filename.pdf argument of chrome browser
 

Image generated using same snapshot as for online case
Original RCanvas is not required

Instead of running complex websocket communication in headless mode,
run chrome browser using file system. 
In that case no any http server is required!

Draft for png, jpg, gif images

Fix problem with connection closure for qt5 web engine
Improve highlights handling for TGraph

One should remove cross-references in destructor, otherwise RWebWindow
object will never get destroyed

Corresponent part of RWebWindow functionality

Support geometry light configuration
Support openui5theme config
Error handling when try object draw in non-existing HTML elements

Small fixes in ROOT7 painting, let correctly use ROOT6 objects inside
RCanvas, including objects update/redraw

This let embed canvas side other ui5 widgets 

Includes several fixes in histogram drawing and redrawing, 
including redrawing of objects from histogram functions list

Update JSROOT code

Plus several fixes in TGeo interface

Avoid too complex binding with RDrawableAttributes.