Fixed parallel issue with task execution logger.

I think it's enough to just use a thead safe map implementation. The execution listener is called from a single thread per single task.
Fixed build action execution where project connection does not point at the root project and using configure-on-demand.
Introduced BasicGradleProject model and use this in GradleBuild model instead of HierarchicalElement.
Fleshed out a few tooling api stories.
A tiny bit more detail for the tooling api changes.
Fixed some typos.
Flipped around the relationship between VersionOnlyBuildEnvironment and DefaultBuildEnvironment.
Moved the new tooling model types into a `gradle` subpackage.
Some javadoc edits.
Merged release branch.