To have the timeline view

This new version has a dependency to libsecret

Also adjust dependencies to the ones from https://github.com/eclipse-theia/theia/blob/v1.16.0/examples/browser/package.json
except api-samples which is not useful.

The client side was reimplemented in node, to workaround segmentation faults
with python/ncurses.

https://github.com/eclipse-theia/theia/blob/v1.8.0/CHANGELOG.md#v180---26112020

https://github.com/eclipse-theia/theia/blob/v1.7.0/CHANGELOG.md#v170---29102020

See https://github.com/eclipse-theia/theia/blob/v1.5.0/CHANGELOG.md#v150---27082020

Use newer nodejs as per requirement

Use vscode extensions for json and plantuml

When updated to 4.8.1 the cursor "shadow" rendering is incorrect

workaround for https://github.com/eclipse-theia/theia/issues/8158

includes vsx registry and our resolution fixes

vscode extensions can no longer be installed from marketplace, but we
can download extensions at installation time.
Install ms-python extension so that we can have good developer
experience with python out of the box.

Also stop including python, as we can use vscode python instead.
Add a README to describe how to do this.

Cloud & Desktop IDE https://www.theia-ide.org/

This version is inspired from "theia-full-docker" from
https://github.com/theia-ide/theia-apps so it includes all extensions.
Many language servers are missing in this version (basically only go,
typescript and python language servers are installed).
PHP extension is not even installed.