Show campaigns (#2113)

* Show campaigns
* Added a ui util class SwipableCardView which passes the onSwipe event to its children
* NearbyCardView & CampaignView extend SwipableCardView
* Fetch campaigns in ContributionsFragment
* Added an option to enable disable campaign in Settings/Preferences

* synced strings with master

* removed duplicate initialsation of CampaignPresenter

app/src/main/java/fr/free/nrw/commons/utils/SwipableCardView.java

@@ -0,0 +1,72 @@
+package fr.free.nrw.commons.utils;
+
+import android.content.Context;
+import android.content.res.Resources;
+import android.support.annotation.NonNull;
+import android.support.annotation.Nullable;
+import android.support.v7.widget.CardView;
+import android.util.AttributeSet;
+import android.util.Log;
+import android.view.MotionEvent;
+import android.view.View;
+
+/**
+ * A card view which informs onSwipe events to its child
+ */
+public abstract class SwipableCardView extends CardView {
+    float x1, x2;
+    private static final float MINIMUM_THRESHOLD_FOR_SWIPE = 100;
+
+    public SwipableCardView(@NonNull Context context) {
+        super(context);
+        interceptOnTouchListener();
+    }
+
+    public SwipableCardView(@NonNull Context context, @Nullable AttributeSet attrs) {
+        super(context, attrs);
+        interceptOnTouchListener();
+    }
+
+    public SwipableCardView(@NonNull Context context, @Nullable AttributeSet attrs,
+        int defStyleAttr) {
+        super(context, attrs, defStyleAttr);
+        interceptOnTouchListener();
+    }
+
+    private void interceptOnTouchListener() {
+        this.setOnTouchListener((v, event) -> {
+            boolean isSwipe = false;
+            float deltaX = 0.0f;
+            Log.e("#SwipableCardView#", event.getAction() + "");
+            switch (event.getAction()) {
+                case MotionEvent.ACTION_DOWN:
+                    x1 = event.getX();
+                    break;
+                case MotionEvent.ACTION_UP:
+                    x2 = event.getX();
+                    deltaX = x2 - x1;
+                    if (deltaX < 0) {
+                        //Right to left swipe
+                        isSwipe = true;
+                    } else if (deltaX > 0) {
+                        //Left to right swipe
+                        isSwipe = true;
+                    }
+                    break;
+            }
+            if (isSwipe && (pixelToDp(Math.abs(deltaX)) > MINIMUM_THRESHOLD_FOR_SWIPE)) {
+                return onSwipe(v);
+            }
+            return false;
+        });
+    }
+
+    /**
+     * abstract function which informs swipe events to those who have inherited from it
+     */
+    public abstract boolean onSwipe(View view);
+
+    private float pixelToDp(float pixels) {
+        return (pixels / Resources.getSystem().getDisplayMetrics().density);
+    }
+}