Allow the Async connection to set some options.

The priority and number of threads can now be set, either through the
DSN configuration or by manually providing those settings in the
constructor.
By default the threads priority will be the lowest possible.
Fix style and indentation
Update the project name description and URL
Move the properties after the project description
Add details on the source/issue/distribution/CI management
Enable reporting

Enables project info, the javadoc, surefire reports, checkstyle and
JXR
Configure contributors and developers

Developers have commit access to the repository while contributors
don't
Enable checkstyle with a local configuration
Add a basic site configuration
Fix typos and links
Update site's configuration

Enable the github ribbon, set-up the pre-release style and display a
link to the parent module