GRADLE-2666: Don't process Gradle plugins and extensions when calculating pom model
Integ test for resolving Ivy dynamic versions with multiple ivyPatterns specified
ExternalResourceResolver no longer implements ivy DependencyResolver
- Introduced separate methods to RepositoryArtifactCache to replace the RepositoryCacheManager methods for ExternalResourceResolver
   - The existing implementations will still be used for native ivy resolvers
- Wrap ExternalResourceResolver in a DependencyResolver for use in parsing (until we switch parsing to Gradle APIs)
- Removed a lot of cruft from ExternalResourceResolver that is no longer required
HTTP-aware version test for resolving 'latest.milestone' against an ivy repository with multiple ivyPatterns
cleanup some archive related tests

- REVIEW-2446/REVIEW-2451: Add more assertions to the duplicateStrategy integration tests
- REVIEW-2446: fix assertZipContainsOnly and move to ZipTestFixture
- REVIEW-2446: create explicit TarTestFixture
- REVIEW-2446: create explicit JarTestFixture and close jarFile properly