Added power button shortcut

app/src/main/AndroidManifest.xml

...rc/main/java/com/speedyapps/keepyousafe/MainActivity.java

...rc/main/java/com/speedyapps/keepyousafe/MapsActivity.java

.../java/com/speedyapps/keepyousafe/PowerButtonReceiver.java

app/src/main/java/com/speedyapps/keepyousafe/SMSManager.java

app/src/main/java/com/speedyapps/keepyousafe/Settings.java

...n/java/com/speedyapps/keepyousafe/confirmationScreen.java

.../main/java/com/speedyapps/keepyousafe/power_receiver.java

app/src/main/res/layout/welcome_side1.xml

app/src/main/res/layout/welcome_side2.xml

app/src/main/res/layout/welcome_side3.xml