Keep demo up to date automatically

[lukaseder]

The demo is currently being kept up to date manually, with the latest versions. This is specifically problematic when trying the commercial demo with the jOOQ trial, which always needs to be up to date. Users then have to first update the version in the demo, rather than just being able to start working (this isn't the case for the OSS edition, which doesn't have to be up to date).

So, the following build process should be added:

• For pro / oss:
  • Limit to recent branches
  • For each branch:
    • Download latest jOOQ version for that branch
    • Check out demo from that branch
    • Update jOOQ version in demo
    • Build demo
    • Check in, if build successful and if there's a diff