Release v0.7.0

chore(release): phd-thesis 0.7.0

This mostly completes the machine learning chapter.

- editing(ML): Move description of problem to results.
- editing(ML): Move intro to ML to start.
- editing(ML): Put citation after punctuation.
- editing(ML): Use numbers over letters for list.
- writing(ML): Introduce machine learning and why.
- editing(Melting): Add citations for Bond order parameters.
- writing(ML): Existing approaches for crystal detection.
- fix(citation): Correct year for citation.
- planning(ML): Move ML algorithms to methods.
- chore(bib): Update bibliography.