Preprocessing scripts for the EstGEC-L2 corpus

Scripts for preprocessing the Estonian L2 Grammatical Error Correction Corpus (EstGEC-L2) that contains L2 learner texts error-annotated in the M2 format.

• convert_conll_to_m2 – used for converting the previous CoNLL-U format error annotation to the M2 format and updating the error tags
• check_m2_annotation – used for validating manual annotation to detect possible format errors
• insert_noop_lines – used for adding the 'noop' annotation to sentences that were not corrected by any of the annotators (the latest version of the converter also adds 'noop' annotations)