Support for user-agent string from AFNetworking library (iOS)

[estemendoza]

AFNetworking it's a great library to handle all the connectivity of an app when developing on iOS.

When using this library, it changes the user-agent to the following format:

<APP_NAME>/<APP_VERSION> (iPhone; iOS 7.1; Scale/2.00)

It would be good that Piwik could support this format because a lot of developers are using this lib.

NOTE: I noted this when importing nginx logs with import_logs.php

[estemendoza]

Other thing to notice is that when implementing this feature, the APP_NAME should be treated as a new browser. I'm saying this because I saw that there's a database of user-agents strings and I think that this would be impossible to maintain due to there's thousands of apps on the AppStore and all they can be a possible "new browser".

[sgiehl]

that will be fixed with 4113164
implementation in piwik might follow