Make it possible to share a domain

we will have one main apache config that includes all the site specific
ones.  All sites sharing this domain should have the same apache config.
Then the site specific stuff goes into the included files.

The deploy scripts should manage this, ensuring the main apache config
file is *always* linked, while the include file might be deleted during
a deploy.

Finally the robots.txt now includes all the admin sites.
Merge pull request #9 from foobacca/shared_apache_config

Make it possible to share a domain

Thanks @foobacca