Updated MGLTilePyramidOfflineRegion documentation to note that local files can’t be used as style URLs. Added documentation for private offline methods.
Also categorized offline symbols for jazzy and moved styleURL from MGLOfflineRegion to MGLTilePyramidOfflineRegion, since you never know if there will be a region type not constrained by a style in the future.
Renamed SDK classes related to offline viewing to more closely match the terminology used by mbgl and the Android SDK while remaining consistent with Cocoa naming principles.
