Going Go1.13.9 -> Go1.13.15 brings in many compiler and runtime fixes,
including security fixes to package net/http:

https://golang.org/doc/devel/release.html#go1.13

Switch helloweb from go1.12 -> go1.13 to test.

Tested on helloworld SR.

Going Go1.12.9 -> Go1.12.17 brings many fixes including security fixes for
net/http package:

https://golang.org/doc/devel/release.html#go1.12

Tested on helloworld SR.

By copy paste mistake wrong log files were configured for log rotation,
resulting with damaging logrotate for the whole partition.

By using nginx it's possible to set it up to expose logs nicely with the
real frontend.

furl is used to rewrite URL from the frontend to add proper username and
password information.

Also use default OpenSSL version.

pyflaked

By using virtio-scsi-pci it's possible to attach many CD-ROMs to be boot from.

Thanks to using to draft-06 schema oneOf the "Boot image" field provides a
list of images to select one to boot.

+minor cleanups user section was not used

Upload files feature uses a websocket at /file-upload , so configure frontends
to allow web sockets on this path.

When using nested slapos $HOME might not be set (which might be a bug in slapos
format) so set $HOME ourselves so that we don't use home files from the outer
slapos.

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

This is current LTS

so that theia can use a local installation of rust using rustup

Introduce an easy way to run slapos commands in a more integrated way.