Teammates: Migrate development tools to Google Cloud SDK

[wkurniawan07]

The development tool stack currently used by us (App Engine SDK, Gradle App Engine Plugin, Google Plugin for Eclipse, Datanucleus for enhancement) is deprecated by Google in favour of Google Cloud SDK and Objectify. One of them has been fixed (kudos @whipermr5!), so the rest should follow suit soon. This will also ease the migration to Java 8 by a significant margin. Edit: I have determined that the SDK and Java 8 are independent.

• [x] [CLI/Gradle](https://cloud.google.com/appengine/docs/standard/java/tools/migrate-gradle)
• [x] [Eclipse](https://cloud.google.com/eclipse/docs/)
• [x] [IntelliJ](https://cloud.google.com/tools/intellij/docs/migrate)

[wkurniawan07]

Just to update progress, this is currently blocked by https://issuetracker.google.com/issues/63732823. Said issue has been fixed and verified by myself by using the latest Google Cloud SDK (171.0.0 at the point of writing), so the work on this shall continue.

[lzzhaha]

Please update the IDE information page concerning the plugin downloading issue

[whipermr5]

@lzzhaha What issue are you referring to? Anyway, the work for this has been done in the teammatesv6 branch (do check if your issue has been resolved there). We have yet to release it as we're waiting to see how this issue develops, so you won't see the changes on the master branch yet.

[lzzhaha]

I mean in that orientation page we are advised to install Google plugin which is deprecated. So I wonder whether I should keep installing that or install Google Cloud SDK instead. Thanks!

[whipermr5]

I believe it has already been fixed (link).

[lzzhaha]

Thank you very much! I have been looking at a wrong page.

[wkurniawan07]

@lzzhaha to clarify, if you wish to set up now, you still need to download the older Google plugins for Eclipse/IntelliJ. If you want to wait for a week or so (hopefully I can release the change by this weekend), then you can follow the new setup instructions.
Alternatively (not advised), you can set up under the teammatesv6 branch and use the more updated plugins for Eclipse/IntelliJ without having to wait.