Changed ExternalResourceResolver so that it does not discard and then later attempt to recreate the meta-data Artifact instance.
Changed ExternalResourceResolver to use ExternalResource instead of Resource.
Changed the parser interfaces so that they don't need to know how to build a metadata Artifact.
Pass an ExternalResource to MetaDataParser rather than an Ivy Resource.
Some minor tidy-ups in the meta-data parser implementations.
Added some more coverage for deprecation messages.
Extracted a common superclass for the archive test fixtures.
Update to the gradle 2.0 spec.