MainActivity: basic UI state restore

app/src/main/java/io/lowrespalmtree/harvestdawn/MainActivity.kt

@@ -61,6 +61,18 @@ class MainActivity : AppCompatActivity() {
         return true
     }
 
+    override fun onSaveInstanceState(outState: Bundle) {
+        outState.putString("cvp", currentVideoPath)
+        outState.putParcelable("cvi", currentVideoUri)
+        super.onSaveInstanceState(outState)
+    }
+
+    override fun onRestoreInstanceState(savedInstanceState: Bundle) {
+        currentVideoPath = savedInstanceState.getString("cvp")
+        currentVideoUri = savedInstanceState.getParcelable("cvi")
+        super.onRestoreInstanceState(savedInstanceState)
+    }
+
     override fun onOptionsItemSelected(item: MenuItem): Boolean {
         // Handle action bar item clicks here. The action bar will
         // automatically handle clicks on the Home/Up button, so long