[android] refactor: Zoom buttons colorized.

android/res/drawable/zoom_in_night.xml

@@ -0,0 +1,9 @@
+<?xml version="1.0" encoding="utf-8"?>
+<selector xmlns:android="http://schemas.android.com/apk/res/android"
+          xmlns:tools="http://schemas.android.com/tools"
+          tools:ignore="UnusedAttribute">
+  <item android:drawable="@drawable/ic_zoom_in_pressed_night"
+        android:state_pressed="true"/>
+
+  <item android:drawable="@drawable/ic_zoom_in_night"/>
+</selector>

android/res/drawable/zoom_out_night.xml

@@ -0,0 +1,9 @@
+<?xml version="1.0" encoding="utf-8"?>
+<selector xmlns:android="http://schemas.android.com/apk/res/android"
+          xmlns:tools="http://schemas.android.com/tools"
+          tools:ignore="UnusedAttribute">
+  <item android:drawable="@drawable/ic_zoom_out_pressed_night"
+        android:state_pressed="true"/>
+
+  <item android:drawable="@drawable/ic_zoom_out_night"/>
+</selector>

android/res/layout/map_navigation_buttons.xml

@@ -25,10 +25,10 @@
   <ImageButton android:id="@+id/map_button_plus"
                style="@style/MwmWidget.MapButton"
                android:layout_marginRight="@dimen/margin_quarter"
-               android:src="@drawable/zoom_in"/>
+               tools:src="@drawable/zoom_in"/>
 
   <ImageButton android:id="@+id/map_button_minus"
                style="@style/MwmWidget.MapButton"
                android:layout_marginRight="@dimen/margin_quarter"
-               android:src="@drawable/zoom_out"/>
+               tools:src="@drawable/zoom_out"/>
 </LinearLayout>

android/src/com/mapswithme/maps/MwmActivity.java

@@ -370,9 +370,13 @@ public class MwmActivity extends BaseMwmFragmentActivity
   {
     View frame = findViewById(R.id.navigation_buttons);
     mBtnZoomIn = (ImageButton) frame.findViewById(R.id.map_button_plus);
+    mBtnZoomIn.setImageResource(ThemeUtils.isNightTheme() ? R.drawable.zoom_in_night
+                                                          : R.drawable.zoom_in);
     mBtnZoomIn.setOnClickListener(this);
     mBtnZoomOut = (ImageButton) frame.findViewById(R.id.map_button_minus);
     mBtnZoomOut.setOnClickListener(this);
+    mBtnZoomOut.setImageResource(ThemeUtils.isNightTheme() ? R.drawable.zoom_out_night
+                                                           : R.drawable.zoom_out);
   }
 
   private void initPlacePage()