This commit adds the generated site for the maven plugin alongside
the developer guide and javadoc. The maven plugin is available in
the "/maven-plugin" context.
The advanced information described in the developer guide have
been migrated to the plugin site as most the information is taken
from the code itself, which avoids duplication.
Fixes#749
Update reference documentation to include a note explaining that
"blessed" versions a chosen based on the gradle plugin version, and
that builds are repeatable.
Fixes gh-619
Stephane Nicoll
Phillip Webb
Dave Syer
Lukasz Kryger