Since Bintray seized operation, the packages for versions 1.4.0 - 1.8.0
have been uploaded to Cloudsmith. Adjust the links appropriately.

An attribution is added to comply with Cloudsmith's OSS hosting policy.

Update the URL to the Gitblit docker image to point to the
`gitblit/gitblit` repository, which I now consider the official
Docker repository.
Also link to the Docker images on the main page.

Ohloh got acquired by Synopsis and is nor Open Hub.
Change the links for the tiny widget to point to Open Hub.

Closes #1356

This is a massive commit which reorganizes the entire project structure
(although it is still monolithic), removes the Build classes, and
switches to Moxie, a smarter Ant build tookit based on the original
Gitblit Build classes.

The Ant build script will likely require additional fine-tuning, but
this is big step forward.