Fix download link and bootstrap

[jackyscript]

Unfortunately building the image is currently not possible, furthermore bootstrapping does not work either.
Kindly refer the following pull request, proposed changes:

• Fix the download link for ApacheDS as the former link is not longer available
  • Former (dead) link: https://downloads.apache.org/directory/apacheds/dist/2.0.0.AM26/apacheds-2.0.0AM26-amd64.deb
  • Changed link to: https://archive.apache.org/dist/directory/apacheds/dist/2.0.0.AM26/apacheds-2.0.0.AM26-amd64.deb
• Extract bootstrapping process from the directory creation process
  • Running the container does not trigger the bootstrapping process, thus resulting in a default root dc dc=example,dc=com (I expected dc=openmicroscopy,dc=org)
  • Instead create the instance directory as necessary and always bootstrap files

EDIT:
Reasoning for not upgrading ApacheDS version:

I refrained from upgrading as there is currently an packaging issue with version AM27, for details check the apache issue tracker here: https://issues.apache.org/jira/browse/DIRSERVER-2389