Removed maybeFailWithConnection { } from tooling API fixtures, replaced by withConnection { }.
Reworked the tooling API provider actions so that serialization problems are not considered build failures.
Added a `GradleBuild` tooling model, which provides details about the basic structure of the build.
Added some methods (with dummy implementations) to `BuildController` to allow models from a particular project to be requested.
Some spec updates.
Fleshed out the `GradleBuild` tooling model.