Talkie: Add preference to disable notifications
android-daemon: Wi-Fi P2P refactoring

Database and GUI removed completely.
Wi-Fi P2P Manager is activated on every start now.
Scanning for peers is done together with the global discovery scheduler.
android-daemon: Drop Wi-Fi P2P support for Android Version < 4.2

This change simplifies the Wi-Fi P2P handling through relying completely
on service discovery provides by Android Jelly Bean.
android-daemon: Check if switch preference is supported (Wi-Fi P2P)
android-daemon: Add service discovery request right before start discovery (Wi-Fi P2P)
android-daemon: Restart P2P discovery if Wi-Fi P2P is enabled again
android-daemon: Add/remove Wi-Fi P2P service request on start/stop discovery
daemon: Only check timestamp constrains if timestamp > 0