Batch-testing for specific errors

[MathiasMehl]

Instead of only having "non-compiling" and "compiling" folders, we could have "flow-error" folder, "type-error" folders, and assert for specific errors

[falkecarlsen]

Multiple approaches:

• Specific folders not nested underneath specific testing-folders for asserting specific exception has been thrown.
• Dynamically assert that each test compilation throws an error of type denoted in header. This would allow a more simple structure.