Set installation to fcm now. (#820)

The push adapter actually ignores the push type and falls back to the device type.  It should be OK to classify these pushes as FCM.

https://github.com/parse-community/parse-server-push-adapter/blob/master/src/PushAdapterUtils.js#L20
https://github.com/parse-community/parse-server-push-adapter/blob/master/src/ParsePushAdapter.js#L35

We should move off the parse-server GCM module because the FCM send only needs the GCloud project instead of sender ID.

Author: rogerhu

fcm/src/main/java/com/parse/fcm/ParseFirebaseJobService.java

@@ -26,6 +26,7 @@
 public class ParseFirebaseJobService extends JobService {
 
     private static final String JOB_TAG_UPLOAD_TOKEN = "upload-token";
+    private static final String PUSH_TYPE = "fcm";
 
     static Job createJob(FirebaseJobDispatcher dispatcher) {
         return dispatcher.newJobBuilder()
@@ -50,7 +51,7 @@ public boolean onStartJob(final JobParameters job) {
         if (installation != null && token != null) {
             installation.setDeviceToken(token);
             //even though this is FCM, calling it gcm will work on the backend
-            installation.setPushType("gcm");
+            installation.setPushType(PUSH_TYPE);
             installation.saveInBackground(new SaveCallback() {
                 @Override
                 public void done(ParseException e) {