Added config property to allow disabling feature

Bug 413867 - Concurrent artifact resolution using same repo session (data) in combination with enhanced local repo can fail sporadically

Made DefaultArtifactResolver call UpdateCheckManager.touchArtifact() only after LocalRepositoryManager.add() to allow concurrent thread to perform required existence check while (enhanced) local repo is in intermediate state

Made DefaultArtifactResolver, DefaultMetadataResolver and DefaultDeployer wrap the user-supplied TransferListener with an instance that captures runtime exceptions and logs them instead of allowing the exception to bubble up and halt the connector

Made DefaultDeployer and DefaultMetadataResolver fill in request trace for *Upload/*Download requests passed to repository connector

Deprecated Transfer.(get|set)State() and added Transfer.(get|set)Listener() instead which allows to employ per-transfer TransferListeners

Made HttpTransporter issue preflight request for initial PUT to init connection-based auth or to gracefully handle premature 100-continue responses

Extended GetTask to optionally carry checksums for downloaded resource and made BasicRepositoryConnector and HttpTransporter make use of it when possible

Improved robustness of expect-continue handling by ensuring user-configured "Expect" header is automatically cleared upon retry if server responded with "Expectation failed"

Made BasicRepositoryConnector only create thread pool when actually multiple requests need processing

Introduced TransferResource.getResumeOffset() to query position at which transfer started

Introduced utility WorkerThreadFactory to help with name customization and made DefaultMetadataResolver as well as BasicRepositoryConnector make use of it

Introduced AuthenticationBuilder.addHostnameVerifier()

Introduced aether-transport-http and dropped aether-connector-asynchttpclient