First pass at NSURLSession-esque auth challenges
Internally switch CKUploader over to new auth challenge delegate method
Switch CKUploader's API over to modern auth handling
Redclare old auth challenge delegate message, but as deprecated
Internally switch CK2OpenPanel to modern auth API
Update open panel's API to modern convention
Correct selector used for open panel auth
Switch to using a block instead of CK2AuthenticationChallengeTrampoline

MASSIVELY simpler!
Protect against clients accidentally calling auth completion handler more than once
Merge branch 'v2.x-beta' into auth-block
Use native protection space rejection when possible
Use native -performDefaultHandlingForAuthenticationChallenge: routine when possible
Merge branch 'v2.x-beta' into auth-block
Merge branch 'v2.x-beta' into auth-block
Merge branch 'v2.x-beta' into auth-block
Vend through server trust challenges from DAVKit
Remove old comment
Match WebDAV transcript newlines to CURL's
Document the transcript delegate
Merge branch 'v2.x-beta' into auth-block