Make small fixes to transcription

Make multiple small fixes based on CR

1. Call validate_intervals() in validate(), call util.validate_intervals() in validate_intervals()
2. Rename match_offsets and match_onsets to match_note_offsets and match_note_onsets
3. Document difference between match_notes, match_not_onsets and match_note_offsets
4. Spellcheck sequences
5. Remove old reference to with_offset parameter from docstring
6. Make OR formula easier to read in docstring
7. Add note about validation in AOR docstring
8. Add beta optional parameter to all functions that compute f1
9. Generate empty interval arrays with correct shape in unit tests

Make PEP8 complient

Update dosctrings for completeness and language consistency