Add tests to be run after adding a new class

[oplatek]

After adding an external dataset

• check wiki that it is helpful
• test loading inputs
• test loading outputs
• test annotations

Document annotation, annotation list structures in the form of tests

# for annotation it should enforce following JSON scheme (ATM)
{
    "reason": "Comment why the text is annotated",
    "text": "The text which is highleted/annotated" ,
    "type": "INDEX_TO_ANNOTATION_LIST_TYPICALLY_IN_METADATA,
    "start": 66,   # index of the character in the annotated output where the annotation starts
}