update WiFi Hotspot support for Nearby Swap

Up until Android 7.0, cc.mvdan.accesspoint:library provided methods for enabling the WiFi Hotspot on a device. That stopped working in Android 7.1. It looks like there is a new technique that will work for Android 8.0 and above: [WifiManager.startLocalOnlyHotspot()](https://developer.android.com/reference/android/net/wifi/WifiManager#startLocalOnlyHotspot(android.net.wifi.WifiManager.LocalOnlyHotspotCallback,%2520android.os.Handler)

This library also claims to do this: https://github.com/vijaypatidar/AndroidWifiManager

And more discussion here:

• https://stackoverflow.com/questions/6394599/android-turn-on-off-wifi-hotspot-programmatically
• https://stackoverflow.com/questions/45984345/how-to-turn-on-off-wifi-hotspot-programmatically-in-android-8-0-oreo

This would also mean that cc.mvdan.accesspoint:library can be removed. It is the only dependency on jcenter, which is going away soon.