Replace illustration for connecting via Bluetooth

briar-android/artwork/bluetooth.svg

briar-android/artwork/il_bluetooth_connect_dark.svg

briar-android/artwork/il_bluetooth_connect_light.svg

...briar/android/contact/connect/BluetoothIntroFragment.java

...roid/src/main/res/drawable-night/il_bluetooth_connect.xml

briar-android/src/main/res/drawable/ic_bluetooth.xml

briar-android/src/main/res/drawable/il_bluetooth_connect.xml

...-android/src/main/res/layout/fragment_bluetooth_intro.xml

...droid/src/main/res/layout/fragment_bluetooth_progress.xml