software/theia: update to 1.9.0 and update extensions
Update to 1.9.0 ( https://github.com/eclipse-theia/theia/blob/v1.9.0/CHANGELOG.md#v190---16122020 )
Update extensions to newer version and to the URLs from openvsx instead of github, since openvsx prevent maintainers to modify releases.
Also use buildout directly to download extensions, so that we verify signatures and have possibility to use cache