#982 ESCET website: add more news teasers + JS loading improvements

• Best to review per commit. Some changes are split over multiple commits, so intermediate commits may not be fully functional.
• End-user visible changes:
  • Added news teasers to Chi, CIF and ToolDef home pages + community page.
  • Load website news asynchronously. Script load is asynchronous. Script executes after DOM is fully available, asynchronously. Improves website load performance.
• Other changes:
  • Moved initNews function from eclipse-escet.js to eclipse-escet-news.js. Renamed eclipse-escet.js to eclipse-escet-versions.js.
  • Renamed ESCET_DEBUG to ESCET_DEBUG_VERSIONS and ESCET_DEBUG_NEWS to avoid duplicate definition in two JS files.
  • Changed website versions loading from onLoad function to inline code. Registered for execution after DOM is fully loaded. Including the file is now enough to get the functionality.
  • Since we now have news teasers in HTML pages that are not in the website root directory, and to ensure proper links to news page for all pages with news teasers, the JavaScript code now looks for a data attribute on the relevant HTML element, to deduce how to create proper links.

Addresses #982