Added a bucketload more Gradle 2.0 candidates after a review of the API.
Tweak to generics on jcenter() method.
Very minor tidy-ups
Deprecated RepositoryHandler.mavenRepo().
Run the JCenter int test only when online.
Deprecated ArtifactRepositoryContainer.add(), addBefore(), addAfter(), addFirst() methods that accept or return an Ivy DependencyResolver.
Updated some int tests for Ivy resolver deprecations.
Only run this int test when online.
Updated Gradle 2.0 plan.
Tweaked the release notes to make it clear we're not dropping support for Ivy, just for Ivy DependencyResolver implementations.
Changed DefaultFlatDirArtifactRepository to use a Gradle ExternalResourceResolver instead of an Ivy FileSystemResolver.
Deprecated a bunch of constants from ArtifactRepositoryContainer.
Inlined some stuff into ResolveIvyFactory, to remove some usages of IvySettings.
Added Transformers.toTransformer() to adapt an Action to a Transformer.
Reworked handling of `Ivy` instances so that each thread resolving or publishing is given its own instance.

- Should fix publishing in parallel execution mode and allow us to use some finer-grained locking during resolution.
- Instances are recycled as the IvySettings instances are relatively expensive to create.
Mark all of the Open API as deprecated. The entry points were deprecated ages ago. This just makes it clearer that the Open API is deprecated.
Wrap artifact resolution in an Ivy context and removed the contextualizing wrapper for each resolver.
Added more @Deprecated annotations to the open API and mention in the release notes.
Some javadoc updates.
Updates to the Gradle 2.0 spec.