Add a double click application

That can be opened by clicking twice.

Closes #34

Also:
+ adjust text color in tutorial
+ some other small adjustments

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

@@ -65,7 +65,6 @@
         android:layout_height="wrap_content"
         android:gravity="center"
         android:onClick="clickAnywhere"
-        android:textColor="#ccc"
         android:textSize="64sp"
         app:layout_constraintBottom_toBottomOf="parent"
         app:layout_constraintEnd_toEndOf="parent"

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

@@ -157,6 +157,29 @@
 
         </TableRow>
 
+        <TableRow
+            android:layout_width="match_parent"
+            android:layout_height="match_parent"
+            android:gravity="center">
+
+            <TextView
+                android:id="@+id/fragment_settings_apps_choose_double_click_text"
+                android:layout_width="match_parent"
+                android:layout_height="wrap_content"
+                android:paddingLeft="10sp"
+                android:paddingRight="10sp"
+                android:text="@string/settings_choose_double_click"
+                android:textSize="20sp" />
+
+            <Button
+                android:id="@+id/fragment_settings_apps_choose_double_click_btn"
+                android:layout_width="wrap_content"
+                android:layout_height="wrap_content"
+                android:text="@string/settings_choose_btn"
+                android:textAllCaps="false" />
+
+        </TableRow>
+
     </TableLayout>
 
     <Button

app/src/main/res/values-de/strings.xml

@@ -21,6 +21,7 @@
     <string name="settings_choose_right">Rechtswischen</string>
     <string name="settings_choose_vol_up">Lautstärke +</string>
     <string name="settings_choose_vol_down">Lautstärke -</string>
+    <string name="settings_choose_double_click">Doppelklick</string>
 
     <string name="settings_choose_btn">App wählen</string>
     <string name="settings_select_launcher">Launcher wählen</string>

app/src/main/res/values-fr/strings.xml

@@ -21,6 +21,7 @@
     <string name="settings_choose_right">Balayez droit</string>
     <string name="settings_choose_vol_up">Monter volume</string>
     <string name="settings_choose_vol_down">Baisser volume</string>
+    <string name="settings_choose_double_click">Double clic</string>
 
     <string name="settings_choose_btn">Choisir App</string>
     <string name="settings_select_launcher">Choisir Launcher</string>

app/src/main/res/values/strings.xml

@@ -29,6 +29,7 @@
     <string name="settings_choose_right">Swipe Right</string>
     <string name="settings_choose_vol_up">Volume Up</string>
     <string name="settings_choose_vol_down">Volume Down</string>
+    <string name="settings_choose_double_click">Double Click</string>
     <string name="settings_choose_btn">Choose App</string>
 
     <string name="settings_select_launcher">Select Launcher</string>