This commit adds the following:
Passkey pairing - passkey is displayed on watch
Swipe down to clear passkey screen
Connection encryption
Connection bonding
Automatic reconnects to a bonded peripheral
Trusted device on Android
Note that persisting the bond between reboots is NOT included in
this commit. Therefore, rebooting the watch will cause reconnect failures.
You must delete the bond from the phone to reconnect/pair.
Don't use relative imports like `../foo.h` as those depend on the
relative position of both files. Rather than that use imports relative
to the `src` directory, which explicitly is part of the include
directories.
Instead of casting the UUID object to the ble_uuid_t* used throughout
the NimBLE API just pass the address of the ble_uuid_t member that's at
the start of each of the UUID structs.
