branch tests are failing

I tried fixing the 8.3.x tests, or at least I wanted to do that. Didn't really manage to.

What I did was:

1. Convert web tests to browser tests
2. Add / fix comments
3. Adhere more strictly to 80 chars rules
4. Convert some of the arrays to short notation (Should be only the ones on lines I had already touched)
5. Fix unit test missing abstract method error.
6. Remove most of the t function calls, the tests don't have translations enabled, so no need to add that overhead
7. Convert some of the deprecated calls to BTB calls.
8. Remove at least some of the randomString calls, using random strings in tests could lead to random fails that are almost impossible to reproduce and debug.

   It's also one of the couple of places where we as devs can add some "personality" to tests. (for example, I added the titles of one of my favorite albums to the search api codebase like that a while ago: http://cgit.drupalcode.org/search_api/tree/tests/src/Functional/HooksTes...) ;)

9. Removed the strict config checking in ManageDisplayTest, this needs to be fixed, but getting green tests is prio #1 I think.

Please help me figure out how to fix the migrate tests, it's the part of Drupal I know the least about and I have no idea why the tests are failing there.

I'm ending my day for now, but I'll come back to this issue over the weekend.

No idea why that's being tested to 8.1.x. should be 8.3.x.

Thx for the patch. I researched the remaining errors, and succeeded in it. Stupid dependencies :). Tests are now green again after the commit :)