Nightly builds moved to Jenkins (Hudson)

Hi everyone

I got tired of managing our BuildBot(s), so I decided to switch our 
continuous integration tool to Jenkins (formerly known as Hudson). You 
find our Jenkins at

   http://gimptest.flamingtext.com:8080/

The main benefits are:
  * An order of magnitude easier to configure and maintain. All
    configuration happens through the web interface.
  * Has its own account and login system, no need for accounts
    on the host machine.
  * One Jenkins for all our projects vs one buildbot per project
  * Mails with last build log lines and list of changes since last
    build works out of the box. That is quite a bit of work to get
    working with buildbot, so much that I gave up on it. In a few days
    I will make failures be posted to gimp-developer, I think that is
    good to do if the mails contains logs and list of changes.

The nightly tarballs can now be reached both through HTTP and FTP with 
permanent URLs:

   babl:

ftp://gimptest.flamingtext.com/pub/nightly-tarballs/babl-git-master.tar.bz2

http://gimptest.flamingtext.com:8080/job/babl-distcheck/lastSuccessfulBuild/artifact/babl-git-master.tar.bz2

   GEGL: