Automate updating the standard visible ESCET website

Currently, we deploy release websites to eclipse.org/escet/<release_version/*. And one of those gets set as the standard visible website at eclipse.org/escet/*. The steps are a bit involved, and manual. This could be automated. The Eclipse TRACE4CPS project has that in place.

Furthermore, with the changes in #386 (closed), the release-specific websites get links to the release-specific pages. It may be good to replace those by standard visible website URLs (thus taking out the version number) when a version-specific website is promoted to standard visible website. An automatic replacement could be done for this.