Updating to Gradle plugin 4.1

[mpodwysocki]

Things to consider before you submit the PR:

• Are tests passing locally?
• Are the files formatted correctly?
• Did you add unit tests?
• Did you test your change with either the sample apps that are included in the repository or with a blank app that uses your change?

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[marstr]

Please delete these lines. We can already use gradle provided version information because of the versionCode and versionName fields above. You can see them already in use here:

azure-notificationhubs-android/notification-hubs-sdk/src/main/java/com/microsoft/windowsazure/messaging/notificationhubs/InstallationPutRequest.java

Lines 138 to 144 in b94ad9f

	private static String getUserAgent() {
	String apiOrigin = "AndroidSdkV1FcmV" + BuildConfig.VERSION_NAME;
	String userAgent = String.format("NOTIFICATIONHUBS/%s (api-origin=%s; os=%s; os_version=%s;)",
	API_VERSION, apiOrigin, "Android", Build.VERSION.RELEASE);
	return userAgent;
	}

[marstr]

gross 😆 Thanks for tracking this down and add a work around

[mpodwysocki]

No longer necessary as we have upgraded Gradle with another commit.