fix(android): properly force quit the application (#57)

Author: edusperoni

app/stop-process.android.ts

@@ -1,3 +1,10 @@
+import { Application } from '@nativescript/core';
+
 export function killProcess() {
+    if(android.os.Build.VERSION.SDK_INT >= 21) {
+        Application.android.startActivity?.finishAndRemoveTask();
+    } else {
+        Application.android.startActivity?.finishAffinity();
+    }
     java.lang.System.exit(0);
 }