Global language support

[tibvdm]

The following YAML is valid and works as intended.

- tab: geefNde
  testcases:
    - expression: 
        haskell: Submission.geefNde 2 [1, 2, 3, 4]
      return: 3

The docs, however, state that I can define the language at the start of the test plan.

- tab: "My tab"
  language: "java"
  testcases:
  - expression: "Submission.toString(1+1)"
    return: "2"

When I try this for the haskell language, Dodona throw an invalid DSL error

- tab: geefNde
  language: haskell
  testcases:
    - expression: Submission.geefNde 2 [1, 2, 3, 4]
      return: 3

[niknetniko]

The docs seem to be wrong; I think it should work like this:

language: haskell
tabs:
- tab: geefNde
  testcases:
    - expression: Submission.geefNde 2 [1, 2, 3, 4]
      return: 3