[android] - expose setAccesToken on Mapbox.java

platform/android/MapboxGLAndroidSDK/src/main/java/com/mapbox/mapboxsdk/Mapbox.java

@@ -68,7 +68,7 @@ public final class Mapbox {
   }
 
   /**
-   * Access token for this application.
+   * Get the current active access token for this application.
    *
    * @return Mapbox access token
    */
@@ -78,6 +78,15 @@ public final class Mapbox {
     return INSTANCE.accessToken;
   }
 
+  /**
+   * Set the current active accessToken.
+   */
+  public static void setAccessToken(String accessToken) {
+    validateMapbox();
+    INSTANCE.accessToken = accessToken;
+    FileSource.getInstance(getApplicationContext()).setAccessToken(accessToken);
+  }
+
   /**
    * Application context
    *