WiFi Fix for iOS 8

Full description of WiFi issues on iOS 8 and Yosemite here:
https://medium.com/@mariociabarra/wifried-ios-8-wifi-performance-issues-3029a164ce94

SpringBoard modified to allow selection in AirDrop
discoveryd modified to prevent D2DWiFi bundle from loading (which prevents AWDL/Air Drop/ etc).
discoveryd_helper (runs as root) modified to bring up and down awdl0 interface (reported to help by @angelXwind)