Refined descriptions of CFNetwork versions of iOS. Added PS 4 UA

I've used http://user-agents.me/cfnetwork-version-list to create a finer grained mapping of CFNetwork/Darwin user agent strings to iOS/Mac OS X Versions. I discovered at least one case where the major version was not mapped correctly and changed to conform to the above named reference.

Also added mappings for iOS 8, iOS 8.0 beta 5 which is just beginning to emerge. These versions do not exist in the above referenced document but we have devices in our lab with these iOS versions and have validated the user agent strings internally.

Separately, identified PlayStation 4 traffic in the field and added a mapping for it.

Regarding the beta versions, I discovered that user_agent_parser.py does not support os_v3_replacement, so I wedged the b5 marker into the os_v2_replacement string. I have a coding change for user_agent_parser.py written to support os_v3_replacement, but decided to hold it back so that this update to CFNetwork could go through even if the coding change to user_agent_parser.py is not acceptable. I will submit that change solo.