Add/Merge additional params on return urls

[Masterjun3]

Resolves the bug where we would redirect to a page with two ?, breaking the query.

To recreate the bug

• go to Submission Catalog
• click New next to Game to create a new game, enter some stuff, and Save
• you get redirected back, notice you're now on a url like /Submissions/Catalog/7251?GameId=2356
• click New next to Game Version to create a new version, enter some stuff, and Save
• you get redirected back again, notice you're now on a url like /Submissions/Catalog/7251?GameId=2356?GameId=2356&GameVersionId=4820

That's the bug, there are two ? in that final link. Only the first ? counts, so the query sets GameId to 2356?GameId=2356.

~~After this PR the final link will look like /Submissions/Catalog/7251?GameId=2356&GameId=2356&GameVersionId=4820. Notice how there are still two GameIds, but it works (and query string expliticly allow multiple settings of the same value).~~

After this PR the final link will look like /Submissions/Catalog/7251?GameId=2356&GameVersionId=4820.

[adelikat]

I like this approach, and the code looks good

[vadosnaprimer]

I'll test locally and call back.

[vadosnaprimer]

If I create game and version, they get properly selected. The baseline goal is created automatically, so I can just select it and save. But if I need to create a different goal and I hit Manage, game version gets unselected.

[Masterjun3]

Technically the Manage button is unrelated to this PR. But I found the reason this happens. It's because our javascript doesn't encode the return url properly. I can make a commit that fixes that as well.

[vadosnaprimer]

Thanks! (it's fixed indeed)