install ruby on the fly

[Mojca Miklavec]

- check if ruby exists
- create a checkbox "I also want to install ruby" (only if there is no ruby installed)
- add directory chooser for ruby
- rsync -av rsync://contextgarden.net/minimals/current/bin/mswin/ruby path/where/ruby/should/be/installed
- set binary path to also include ruby binaries

Another option is to install this one:
    http://rubyforge.org/projects/rubyinstaller/
(http://rubyforge.org/frs/download.php/29263/ruby186-26.exe, but you need to keep your info about ruby version up to date)

Mojca