feat(Android): Support Android file upload (#60)

Fixes #33 

I could really use some help from an Android developer on this one, because I just "made it work", don't know how to "make it work good".

Some things that should be reviewed:

- [ ] validate Android 5.0 devices (my emulator work, but outputs some weird sounds; a Galaxy 4 I tested on crashes)
- [ ] validate Android 5.1 devices (emulator works, couldn't find a real device)
- [ ] how to handle File Extensions? (https://www.w3schools.com/tags/att_input_accept.asp)

I'm sure that there's more refactoring to be done, so any help and advice would be appreciated.

android/src/main/java/com/reactnativecommunity/webview/RNCWebViewPackage.java

@@ -1,6 +1,7 @@
 
 package com.reactnativecommunity.webview;
 
+import java.util.ArrayList;
 import java.util.Arrays;
 import java.util.Collections;
 import java.util.List;
@@ -10,10 +11,19 @@ import com.facebook.react.bridge.NativeModule;
 import com.facebook.react.bridge.ReactApplicationContext;
 import com.facebook.react.uimanager.ViewManager;
 import com.facebook.react.bridge.JavaScriptModule;
+
 public class RNCWebViewPackage implements ReactPackage {
+
+    private RNCWebViewManager manager;
+    private RNCWebViewModule module;
+
     @Override
     public List<NativeModule> createNativeModules(ReactApplicationContext reactContext) {
-      return Arrays.<NativeModule>asList(new RNCWebViewModule(reactContext));
+      List<NativeModule> modulesList = new ArrayList<>();
+      module = new RNCWebViewModule(reactContext);
+      module.setPackage(this);
+      modulesList.add(module);
+      return modulesList;
     }
 
     // Deprecated from RN 0.47
@@ -23,7 +33,12 @@ public class RNCWebViewPackage implements ReactPackage {
 
     @Override
     public List<ViewManager> createViewManagers(ReactApplicationContext reactContext) {
-        RNCWebViewManager viewManager = new RNCWebViewManager();
-        return Arrays.<ViewManager>asList(viewManager);
+      manager = new RNCWebViewManager();
+      manager.setPackage(this);
+      return Arrays.<ViewManager>asList(manager);
     }
-}
+
+    public RNCWebViewModule getModule() {
+      return module;
+    }
+}